ENVIRONMENTAL
CONTROL
IN
PETROLEUM
ENGINEERING
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ENVIRONMENTAL
CONTROL
IN
IN
PETR OLEUM
ENGINEERING
JOHN C. REIS
Gulf Publishing Company
Houston, London, Paris, Zurich, Tokyo
ENVIRONMENTAL CONTROL
IN PETROLEUM ENGINEERING
Copyright © 1996 by Gulf Publishing Company,
Houston, Texas. All rights reserved. Printed in the
United States of America. This book, or parts thereof,
may not be reproduced in any form without permission
of the publisher.
Gulf Publishing Company
Book Division
P.O. Box 2608 n Houston, Texas 772522608
10 9 8 7 6 5 4
3
21
Library of Congress Cataloging-in-Publication Data
Reis, John C.
Environmental control in petroleum engineering /
John C. Reis.
p.
cm.
Includes bibliographical references and index.
ISBN 0-88415-273-1 (alk. paper)
1. Petroleum engineering—Environmental
aspects. 2. Pollution. I. Reis, John C. II. Title.
TD195.P4R45 1996
665.6—dc20
9548462
CIP
Printed on AcidFree Paper (°°)
Contents
Acknowledgments
viii
Preface
ix
CHAPTER 1
ntroduction to Environmental Control
n the Petroleum Industry
Overview of Environmental Issues, 2.
References, 16.
1
A New Attitude. 11.
CHAPTER 2
Drilling and Production Operations
Drilling, 18. Production. 39.
References, 65.
18
Air Emissions, 57.
CHAPTER 3
The Impact of Drilling and Production Operations
71
Measuring Toxicity, 71. Hydrocarbons, 77. Salt, 96.
Heavy Metals, 100. Production Chemicals, 105.
Drilling Fluids, 106. Produced Water, 120. Nuclear
Radiation, 121. Air Pollution, 126. Acoustic Impacts, 127.
Effects of Offshore Platforms, 128. Risk Assessment, 128.
References, 131.
CHAPTER 4
Environmental Transport of Petroleum Wastes
Surface Paths, 139. Subsurface Paths, 140.
Paths, 142. References, 142.
139
Atmospheric
CHAPTER 5
Planning for Environmental Protection
.144
Environmental Audits, 145. Waste Management Plans, 149.
Waste Management Actions, 151. Certification of Disposal
Processes, 162. Contingency Plans, 163. Employee
Training, 165. References, 166.
CHAPTER 6
Waste Treatment Methods
172
Treatment of Water, 172. Treatment of Solids, 185.
Treatment of Air Emissions, 194. References, 196.
CHAPTER 7
Waste Disposal Methods
Surface Disposal, 203.
References, 212.
.......203
Subsurface Disposal, 207.
CHAPTER 8
Remediation of Contaminated Sites..
Site Assessment, 216.
References, 226.
....216
Remediation Processes, 220.
APPENDIX A
Environmental Regulations......
230
United States Federal Regulations, 231. State
Regulations, 249. Local Regulations, 249. Regulations
in Other Countries, 249. Cost of Environmental
Compliance, 250. References, 251.
APPENDIX B
Sensitive Habitats
Rain Forests, 256.
256
Arctic Regions, 257.
References, 257.
APPENDIX C
Major U.S. Chemical Waste Exchanges
..258
APPENDIX D
Offshore Releases of Oil
Natural Dispersion of Oil, 261.
of Oil, 264. References, 268.
ndex
261
Enhanced Removal
271
Acknowledgments
I would like to thank the many students who provided feedback on
the course notes that eventually lead to this book. I would also like
o thank Larry Henry for his thoughtful review of the manuscript. I
gratefully acknowledge the donation of the reports by the American
Petroleum Institute that are cited in this book.
Preface
With the rise of the environmental protection movement, the
petroleum industry has placed greater emphasis on minimizing the
environmental impact of its operations. Improved environmental
protection requires better education and training of industry personnel.
There is a tremendous amount of valuable information available on
he environmental impact of petroleum operations and on ways to
minimize that impact; however, this information is scattered among
housands of books, reports, and papers, making it difficult for industry
personnel to obtain specific information on controlling the environ
mental effects of particular operations. This book assembles a sub
tantial portion of this information into a single reference.
The book has been organized and written for a target audience
having little or no training in the environmental issues facing the
petroleum industry. The first chapter provides a brief overview of these
ssues. The second chapter focuses on the various aspects of drilling
and production operations, while the third chapter discusses the
pecific impacts associated with them. Chapter 4 discusses ways in
which toxic materials can be transported away from their release sites.
Actual waste transport modeling is a very complex topic and
s beyond the scope of this book.) The fifth chapter presents ways
o plan and manage activities that minimize or eliminate potential
nvironmental impacts without severely disrupting operations.
The sixth chapter discusses the treatment of drilling and production
wastes to reduce their toxicity and/or volume before ultimate disposal.
Chapter 7 presents disposal methods for various petroleum industry
wastes. The final chapter reviews available technologies for remediat
ng sites contaminated with petroleum wastes. A summary of major
United States federal regulations, a list of major U.S. chemical waste
xchanges, and discussions of sensitive habitats and offshore releases
of oil are provided in the appendixes.
This book has evolved from course notes developed by the author
or use in undergraduate and graduate classes. In preparing the book,
he author has read thousands of pages of papers, reports, manuals,
and books on the topic of environmental concerns facing the upstream
petroleum industry. Although it is believed that this book is technically
accurate, some errors and omissions have invariably occurred. There
are many excellent papers and studies that are not included because
he author did not become aware of them prior to publication of the
book. The author welcomes constructive comments that may improve
uture editions.
ENVIRONMENTAL
CONTROL
IN
PETROLEUM
ENGINEERING
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CHAPTER 1
Introduction to
Environmental
Control in the
Petroleum Industry
The upstream petroleum industry, which conducts all exploration
and production activities, provides essential petroleum products that
are used for transportation fuels, electrical power generation, space
heating, medicine, and petrochemicals. These uses of petroleum are
major contributors to our present standard of living. The activities of
inding and producing petroleum, however, can impact the environ
ment, and the greatest impact arises from the release of wastes into
he environment in concentrations that are not naturally found. These
wastes include hydrocarbons, solids contaminated with hydrocarbons,
water contaminated with a variety of dissolved and suspended solids,
and a wide variety of chemicals. While some of these wastes can have
ignificant adverse effects on the environment, some have little impact,
and others are actually beneficial. In virtually all cases, the adverse
mpact can be minimized or eliminated through the implementation
of proper waste management.
The most important steps in minimizing adverse environmental
mpact are for the industry to take a proactive approach to managing
operations and become educated about those activities that can potentially
harm the environment. The proactive approach involves adopting an
attitude of environmental responsibility—not just to comply with
egulations but to actually protect the environment while doing business.
2
Environmental Control in Petroleum Engineering
1.1 OVERVIEW OF ENVIRONMENTAL ISSUES
Finding and producing oil and gas while minimizing adverse environ
mental impact requires an understanding of the complex issues facing
he upstream petroleum industry. These issues concern operations that
generate wastes, their potential influence on the environment, mech
anisms and pathways for waste migration, effective ways to manage
wastes, treatment methods to reduce their volume and/or toxicity,
disposal methods, remediation methods for contaminated sites, and all
applicable regulations.
1.1.1
Sources of Wastes
Wastes are generated from a variety of activities associated with
petroleum production. These wastes fall into the general categories of
produced water, drilling wastes, and associated wastes. Produced water
accounts for about 98% of the total waste stream in the United States,
with drilling fluids and cuttings accounting for the remaining 2%.
Other associated wastes combined contribute a few tenths of a percent
o the total waste volume (American Petroleum Institute, 1987). The
otal volume of produced water in the United States is roughly 21
billion barrels per year (Perry and Gigliello, 1990). A typical well can
generate several barrels of fluid and cuttings per foot of hole drilled.
In 1992, 115,903,000 feet of hole were drilled in the United States
(American Petroleum Institute, 1993), yielding on the order of 300
million barrels of drilling waste.
Produced water virtually always contains impurities, and if present
n sufficient concentrations, these impurities can adversely impact the
environment. These impurities include dissolved solids (primarily salt
and heavy metals), suspended and dissolved organic materials, forma
ion solids, hydrogen sulfide, and carbon dioxide, and have a defi
ciency of oxygen (Stephenson, 1992). Produced water may also contain
ow levels of naturally occurring radioactive materials, or NORM
(Gray, 1993). In addition to naturally occurring impurities, chemical
additives like coagulants, corrosion inhibitors, emulsion breakers,
biocides, dispersants, paraffin control agents, and scale inhibitors are
often added to alter the chemistry of produced water. Water produced
rom waterflood projects may also contain acids, oxygen scavengers,
Introduction to Environmental Control in the Petroleum Industry
3
surfactants, friction reducers, and scale dissolvers that were initially
njected into the formation (Hudgins, 1992).
Drilling wastes include formation cuttings and drilling fluids. Water
based drilling fluids may contain viscosity control agents (e.g., clays),
density control agents, (e.g., barium sulfate, or barite), deflocculants,
(e.g., chromelignosulfonate or lignite), caustic (sodium hydroxide),
corrosion inhibitors, biocides, lubricants, lost circulation materials, and
formation compatibility agents. Oilbased drilling fluids also contain
a base hydrocarbon and chemicals to maintain its waterinoil emul
sion. The most commonly used base hydrocarbon is diesel, followed
by less toxic mineral and synthetic oils. Drilling fluids typically
contain heavy metals like barium, chromium, cadmium, mercury, and
lead. These metals can enter the system from materials added to the
fluid or from naturally occurring minerals in the formations being
drilled through. These metals, however, are not typically bioavailable,
An extensive discussion of the environmental impacts of drilling
wastes has been presented by Bleier et al. (1993).
Associated wastes are those other than produced water and drilling
wastes. Associated wastes include the sludges and solids that collect
n surface equipment and tank bottoms, pit wastes, water softener
wastes, scrubber wastes, stimulation wastes from fracturing and acidiz
ng, wastes from dehydration and sweetening of natural gas, transporta
ion wastes, and contaminated soil from accidental spills and releases.
Another waste stream associated with the petroleum industry is air
emissions. These emissions arise primarily from the operation of
nternal combustion engines. These engines are used to power drill
ng rigs, pumps, compressors, and other oilfield equipment. Other
emissions arise from the operations of boilers, steam generators,
natural gas dehydrators, and separators. Fugitive emissions from
eaking valves and fittings can also release unacceptable quantities of
volatile pollutants.
One common, but incorrect, perception of the petroleum exploration
and production industry is that it is responsible for largescale hydro
carbon contamination of the sea. The total amount of hydrocarbons
hat enter the sea is estimated to be 3.2 million metric tons per year,
The individual contributions from the different sources of hydrocarbons
s given in Table 11 (National Research Council, 1985). The primary
source of hydrocarbon releases into the ocean is from transportation
Environmental Control in Petroleum Engineering
Table 1-1
Sources of Hydrocarbon Inputs into the Sea
Source
Natural Sources
Marine seeps
Sediment erosion
Offshore Production
Transportation
Tanker operations
Drydocking
Marine terminals
Bilge and fuel oils
Tanker accidents
Nontanker accidents
Atmospheric Transport
Municipal and Industrial
Municipal wastes
Refineries
Nonrefining industrial wastes
Urban runoff
River runoff
Ocean dumping
TOTAL
Amount Introduced
(metric tons/year)
0.25
(0.2)
(0.05)
0.05
1.47
(0.7)
(0.03)
(0.02)
(0.3)
(0.4)
(0.02)
0.3
1.18
(0.7)
(0.1)
(0.2)
(0.12)
(0.04)
(0.02)
3.2
Source: from National Research Council, 1985.
Copyright © 1985, National Academy of Sciences.
Courtesy of National Academy Press, Washington, D.C.
by tankers. Oil production from offshore platforms contributes less
than 2% of the total amount of oil entering the sea.
1.1.2
Environmental Impact of Wastes
The primary measure of the environmental impact of petroleum
wastes is their toxicity to exposed organisms. The toxicity of a sub
stance is most commonly reported as its concentration in water that
results in the death of half of the exposed organisms within a given
length of time. Exposure times for toxicity tests are typically 96 hours.
Introduction to Environmental Control in the Petroleum Industry
5
although other times have been used. Common test organisms include
mysid shrimp or sheepshead minnows for marine waters and fathead
minnows or rainbow trout for fresh waters.
The concentration that is lethal to half of the exposed population
during the test is called LC50. High values of LC50 mean that high
concentrations of the substance are required for lethal effects to be
observed, and this indicates a low toxicity. A related measure of
toxicity is the concentration at which half of the exposed organisms
exhibit sublethal effects; this concentration is called EC50. Another
measure of toxicity is the no observable effect concentration (NOEC),
the concentration below which no effects are observed.
The environmental impact of hydrocarbons in water varies consider
ably (National Research Council, 1985). The toxicity of aromatic
hydrocarbons is relatively high, while that of straightchain paraffins
is relatively low. LC50 values for the most common aromatic hydro
carbons found in the petroleum industry (benzene, toluene, xylene, and
ethylbenzene) are on the order of 10 ppm. Hydrocarbon concentrations
of less than 1 mg/1 in water have been shown to have a sublethal
impacts on some marine organisms. High molecular weight paraffins,
on the other hand, are essentially nontoxic. Chronic exposures of entire
ecosystems to hydrocarbons, either from natural seeps or from petro
leum facilities, have shown no long or intermediateterm impact; the
ecosystems have all recovered when the source of hydrocarbons was
removed. No evidence of irrevocable damage to marine resources on
a broad oceanic scale, by either chronic inputs or occasional major
oil spills, has been observed. Although there are shortterm impacts
from major, spills, the marine resources can and do recover.
Other effects of hydrocarbons include stunted plant growth if the
hydrocarbon concentration in contaminated soil is above about 1% by
weight. Lower concentrations, however, can enhance plant growth
(Deuel, 1990). Hydrocarbons can also impact higher organisms that
may become exposed following an accidental release. Marine animals
that use hair or feathers for insulation can die of hypothermia if coated
with oil. Coated animals can also ingest fatal quantities of hydro
carbons during washing and grooming activities.
The high dissolved salt concentration of most produced water can
also impact the environment. Typical dissolved salt concentrations for
produced water range between 50,000 and 150,000 ppm. By compari
son, the salt concentration in seawater is about 35,000 ppm. Dissolved
6
Environmental Control in Petroleum Engineering
salt affects the ability of plants to absorb water and nutrients from soil.
t can also alter the mechanical structure of the soil, which disrupts
he transport of air and water to root systems. Water with dissolved
salt concentrations below about 2,500 mg/1 have minimal impact on
most plants (Deuel, 1990). LC50 values for dissolved salt concen
rations for freshwater organisms are on the order of 1,000 ppm.
(Mount et al., 1993).
The toxicity of drilling muds varies considerably, depending on
heir composition. Toxicities (LC50) of waterbased muds containing
small percentages of hydrocarbons can be a few thousand ppm. The
LC50s of polymer muds, however, can exceed one million, which
means that fewer than 50% of a test species will have died during
he test period.
The toxicity of heavy metals found in the upstream petroleum
ndustry varies widely. The toxicity of many heavy metals lies in their
nterference with the action of enzymes, which limits or stops normal
biochemical processes in cells. General effects include damage to the
iver, kidney, or reproductive, blood forming, or nervous systems. With
some metals, these effects may also include mutations or tumors,
Heavy metal concentrations allowed in drinking water vary for each
metal, but are generally below about 0.01 mg/L. The heavy metals in
offshore drilling fluid discharges normally combine quickly with the
naturally abundant sulfates in seawater to form insoluble sulfates and
precipitates that settle to the sea floor. This process renders the heavy
metals inaccessible for bioaccumulation or consumption.
Nuclear radiation from NORM can disrupt cellular chemistry and
alter the genetic structure of cells. In most cases, however, radiation
exposure from NORM is significantly lower than that from other
natural and manmade sources of radiation and does not represent a
serious health hazard (Snavely, 1989).
The various chemicals used during production activities can also
affect the environment. Their toxicities vary considerably, from highly
toxic to essentially nontoxic. In most cases, however, the concen
trations of chemicals actually encountered in the field are below toxic
levels (Hudgins, 1992).
The primary environmental consequences of air pollutants are
respiratory difficulties in humans and animals, damage to vegetation,
and soil acidification. Releases of hydrogen sulfide, of course, can be
fatal to those exposed.
Introduction to Environmental Control in the Petroleum Industry
7
1.1.3 Waste Migration
In most cases, the environmental impact of released wastes would
be minimal if the wastes stayed at the point of release; unfortunately,
most wastes migrate from their release points to affect a wider area.
The migration pathway most often moves through groundwater along
the local hydraulic gradient. For releases at sea, wastes will follow
the prevailing winds and currents. For air emissions, the pollutants will
follow the winds. Because migration spreads the wastes over a wider
area, the local concentrations and toxicities at any location will be
reduced by dilution.
1.1.4 Managing Wastes
The most effective way to minimize environmental impact from
drilling and production activities is to develop and implement an
effective waste management plan. Waste management plans identify
the materials and wastes at a particular site and list the best way to
manage, treat, and dispose of those wastes (Stilwell, 1991; American
Petroleum Institute, 1989). A waste management plan should also
include an environmental audit to determine whether existing activities
are in compliance with relevant regulations (Guckian et al., 1993),
The effective management of each waste consists of a hierarchy of
preferred steps. The first and usually most important step is to mini
mize the amount and/or toxicity of the waste that must be handled.
This is done by maintaining careful control on chemical inventories,
changing operations to minimize losses and leaks, modifying or
replacing equipment to generate less waste, and changing the processes
used to reduce or eliminate the generation of toxic wastes.
The next step in effective waste management is to reuse or recycle
wastes. If wastes contain valuable components, those components can
be segregated or separated from the remainder of the waste stream and
recovered for use. Wastes that cannot be reused or recycled must then
be treated and disposed of. A written waste management plan that
completely describes the acceptable options for handling every waste
generated at every site must be developed and effectively communi
cated to every employee involved with the wastes. Examples of how
the waste management hierarchy can be implemented are given by
Thurber (1992), Derkies and Souders (1993), and Savage (1993).
8
Environmental Control in Petroleum Engineering
In most cases, the cost of eliminating all risks and hazards associ
ated with wastes is economically prohibitive. Prudent management
practices focus available resources on the activities that pose the
greatest risk to both the economic health of the company and the
environment. The risks associated with various waste management
practices can be quantified and ranked through risk assessment studies
Sullivan, 1991). When properly managed, the risks and hazards of
drilling and production operations can be reduced to low levels.
1.1.5
Waste Treatment Methods
Most wastes require some type of treatment before they can be
disposed of. Waste treatment may include reducing the waste's total
volume, lessening its toxicity, and/or altering its ability to migrate
away from its disposal site. A variety of treatment methods are
available for different types of wastes, although their costs vary
significantly. The waste treatment method selected, however, must
comply with all regulations, regardless of their cost.
One of the most important steps in waste treatment is to segregate
or separate the wastes into their constituents, e.g., solid, aqueous, and
hydrocarbon wastes. This isolates the most toxic component of the
waste stream in a smaller volume and allows the less toxic components
o be disposed of in less costly ways. Primary separation occurs with
properly selected and operated equipment, e.g., shale shakers, separa
ion tanks, and heater treaters. Separation can be improved by using
hydrocyclones, filter presses, gas flotation systems, or decanting
centrifuges (Wojtanowicz et al., 1987). In arid areas, evaporation
and/or percolation can be used to dewater some wastes.
A number of methods are available for treating hydrocarbon
contaminated solids like drill cuttings, produced solids, or soil. Solids
can be washed by agitation in a jet of highvelocity water, perhaps
with an added surfactant. Solids can also be mixed with an oilwet
material such as coal or activated carbon, that absorbs the hydrocar
bons and can be separated from the more dense solids by subsequent
lotation. An emerging and promising technology for hydrocarbon
emoval from contaminated solids is bioremediation. Other treatment
methods include distillation, solvent extraction, incineration, and
critical/supercritical fluid extraction.
Introduction to Environmental Control in the Petroleum Industry
§
Nonhydrocarbon aqueous wastes can be treated by a number of
methods, including ion exchange, precipitation, reverse osmosis,
evaporation/distillation, biological processes, neutralization, and solidi
fication. These processes can remove dissolved solids from water
or encase them in other solids to prevent subsequent leaching follow
ing disposal.
1.1.6
Waste Disposal Methods
A number of disposal methods are available for petroleum industry
wastes. The method used depends on the type, composition, and
regulatory status of the waste.
The primary disposal method for aqueous wastes is to inject them
into Class II wells. If the quality of wastewater meets or exceeds
regulatory limits, permits to discharge it into surface waters may be
obtained in some areas.
The primary disposal methods for solid wastes are to bury them or
to spread them over the land surface. All free liquids normally must
be removed prior to disposal, either by mechanical separation, evapora
tion, or the addition of solidifying agents. Land treatment of wastes
may be prohibited if volatile and leachable fractions are present in the
wastes. Disposal can occur either on or offsite. Underground injection
of slurries has also been used for solids disposal in some areas.
1.1.7 Cleanup Methods for Contaminated Sites
The most appropriate cleanup method will depend on the contami
nant and on the site characteristics. The most common contaminated
sites are those that have spilled hydrocarbons in the soil and those
containing old drilling fluids.
A number of methods can be used to clean up sites. Mobile hydro
carbons can be removed by drilling wells or digging trenches and
pumping the hydrocarbons to the surface with groundwater for treat
ment. Volatile hydrocarbons can be removed by injecting air and/or
pulling a vacuum to vaporize those components. The use of heat,
surfactants, and bioremediation to remove subsurface hydrocarbons is
being studied. Dissolved hydrocarbons in water and volatilized hydro
carbons in air can be removed by filtration or by absorption with
10
Environmental Control in Petroleum Engineering
activated carbon. In some cases, however, the contaminated material
may need to be completely removed for off site treatment and disposal.
1.1.8
Environmental Regulations
One of the most significant changes occurring in the operations of
he upstream petroleum industry during the 1980s has been the need
o minimize environmental impact. This change has been driven by
an increase in the number of regulations governing drilling and
production activities. Most of these regulations impose economic fines
and possibly criminal penalties for violations. These regulations have
significantly increased the cost of industry operations.
Major United States Environmental Regulations and Costs
A number of major environmental regulations affect the operation
of petroleum exploration and production activities in the United States
(Gilliland, 1993; Interstate Oil Compact Commission, 1990). Some of
hese regulations are briefly reviewed below; a more extensive discus
sion of the regulations is included in Appendix A.
The Resource Conservation and Recovery Act (RCRA), Subtitle C,
regulates the storage, transport, treatment, and disposal of hazardous mate
ials that are intended to be discarded, i.e., wastes. This regulation defines
hazardous wastes as those that are specifically listed by name or those
hat are either highly reactive, corrosive, flammable, or toxic. Most, but
not all, upstream petroleum industry wastes are exempt from this regulation.
The Safe Drinking Water Act was passed to protect underground
sources of drinking water (USDW). This act regulates activities that
may contaminate USDWs, particularly injection wells for both oil
ecovery and water disposal, as well as the plugging of abandoned
wells. This act requires regular mechanical integrity testing of all
njection wells.
The Clean Water Act prohibits the discharge of wastes, particularly
oil, into surface waters or drainage features that may lead to surface
waters. This act requires many operators to prepare spill prevention
control and countermeasure (SPCC) plans to help minimize the impact
of any spills.
The Clean Air Act regulates the emissions of air pollutants, includ
ng exhaust from internal combustion engines, fugitive emissions, and
Introduction to Environmental Control in the Petroleum Industry
11
boiler emissions. This act specifies the types of emissions control
equipment that must be used.
The Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA or Superfund) was enacted to identify existing
sites where hazardous wastes may impact human health. It established
cleanup and claims procedures for affected parties. The Superfund
Amendments and Reauthorization Act (SARA) requires that facilities
storing hazardous materials keep a written inventory of those materials
and provide them to local authorities. Crude oil is considered non
hazardous under this act, while many of the other RCRA exempt
wastes are considered hazardous.
The potential costs of environmental regulations on the exploration
and production of oil have been studied (Godec and Biglarbigi, 1991;
Perkins, 1991). Depending on how these regulations are interpreted
and implemented, the resulting loss of production may be as high as
50% of that without the environmental regulations. If the economic
costs of these regulations in the U.S. is prorated over the existing
production levels, the resulting costs would be a few dollars per barrel
of oil produced.
1.2 A NEW ATTITUDE
We are all environmentalists. We all want a clean place to live. We
all want clean water to drink. We all want clean air to breath. We all
want to live in a world safe from toxic hazards. We all want to live
in a world that is aesthetically pleasing. Yet, we also want the benefits
of inexpensive energy. We want to be able to drive our cars, fly our
planes, have electric lights and appliances in our homes, and keep our
homes warm in the winter and cool in the summer. We want the
medicines and plastics made from hydrocarbons. But often, the desire
for a pristine environment and the benefits of inexpensive energy
conflict. To drive our cars, we must find, produce, and transport crude
oil. To maintain access to the benefits of inexpensive energy, we need
a strong domestic petroleum industry.
There will always be the risk of environmental harm during explora
tion and production activities. There are risks associated with all
human activities and a balance must be struck between the risks and
benefits of those activities. Fortunately, virtually all activities of the
upstream petroleum industry have effective technical options that can
12
Environmental Control in Petroleum Engineering
minimize or eliminate their environmental risks. Unfortunately, many
of those options are expensive and may not be economically possible.
One of the keys to producing oil in environmentally responsible
ways is to be aware of any potential hazards and to plan effective ways
o minimize those hazards before a particular project begins. The first
step in this process is education. Petroleum engineers, geologists, and
managers must understand the place their industry occupies in society.
All companies, including oil companies, exist by the grace and will
of the people in society. If society does not want an industry to exist,
hat industry can be shut down, either through legislation, litigation,
or economic boycotts. Unfortunately, the social pressures imposed on
an industry are not necessarily based on accurate scientific information,
Many existing regulations are politically based and do little to protect
human health and the environment, yet they add considerable costs
o businesses that must comply.
The environmental movement that has arisen over the past few
decades has resulted in regulations that have had a profound effect
on the operations of the upstream petroleum industry. These regulations
have been imposed because the public no longer believes that the
ndustry can regulate itself and still protect the environment. Some of
his loss of confidence has been earned, but some is the result of
deliberate misinformation spread by environmental extremists and a
media willing to misrepresent the truth to sell copy.
Regardless of why the public lacks confidence in the ability of the
petroleum industry to operate in an environmentally responsible
manner, the industry must adapt and learn to live within the increas
ngly tight environmental regulations in order to survive. The funda
mental shift in attitude toward proactive environmental protection that has
begun must continue—the past ways of doing business are gone and will
not return. It is not enough just to comply with whatever the current
regulations might be; there must be a serious commitment toward protect
ng the environment in all activities, regardless of the regulations.
The key to effective regulations that protect the environment is for
he regulations to be based on accurate scientific information. If an
ndustry has lost its credibility with the public regarding environmental
concerns due to its past behavior, then any accurate scientific informa
ion about the environmental impact of its current operations will also
ack credibility. This results in regulations that are very costly to the
ndustry, but do little to protect the environment.
Introduction to Environmental Control in the Petroleum Industry
13
Because funds available for environmental compliance are limited
to those received within a project's minimum profitability level, these
funds should be spent in ways that provide maximum protection
for the environment. Bad regulations can require that available funds
be spent in ways that provide little environmental protection. This
increases the cost of doing business and can make many marginal projects
uneconomical, resulting in a loss of jobs and reduction in domestic
production. Thus, the conflict between the benefits of inexpensive energy
and environmental protection are magnified by bad regulations.
The following hypothetical situation illustrates how misinformation
and misunderstanding about sound scientific environmental principles
can lead to the economic destruction of an industry:
A company applied for a discharge permit for a process and
reported that the effluent concentrations of a particular chemical
would be 75 parts per thousand. The discharge permit was denied
on the grounds that the effluent concentration was too high. The
company then spent thousands of dollars to upgrade their waste
treatment stream and reduced the effluent concentration to 75
parts per million. Their discharge permit was again denied on the
same grounds. The company then spent millions of dollars more
to install the best available technology for treating the waste
effluent. They successfully reduced the discharge concentration
to 75 parts per billion. Unfortunately, the discharge permit was
again denied on the grounds that the effluent concentration was
still to high. The company then invested billions of dollars in
research and development to create a new way to treat the
effluent and lower the discharge concentration to 75 parts per
trillion. The discharge permit was again denied. At this point, the
company went bankrupt and was forced out of business because
it spent all of its money trying to comply with environmental
regulations. When they asked the permitting agency why their
discharge permits were denied, they were simply told that 75
parts was just too high.
Although this story incorrectly implies that regulatory agencies do not
base their regulations on sound scientific principles, the sad truth is
that regulatory agencies must operate within laws passed by people
who may lack an understanding of scientific environmental principles.
14
Environmental Control in Petroleum Engineering
One industry that has been effectively destroyed by social pressure
resulting from environmental misinformation is the nuclear power
industry in the United States, even though the actual risks from nuclear
power can be significantly lower than those from other, more accept
able forms of electrical power, such as coal. If the domestic petroleum
industry completely loses the confidence of the public, it too can be
effectively destroyed. If this occurs, then the imports of crude oil and
products will increase significantly. Ironically, the transportation of
imported crude oil creates a much greater environmental hazard than
domestic production.
Historically, the petroleum industry has reacted often to new regula
tions by changing operational practices the minimum amount required
to meet the letter of the regulations. But because of the complex,
rapidly changing regulatory environment, this approach can no longer
be used productively. Activities that comply completely with today's
regulations can result in significant liability tomorrow.
Perhaps the most important thing the petroleum industry can do is
adopt an attitude of working in harmony with the public will. Regula
ory agencies should not be viewed as enemies but as coworkers in
an effort to produce oil in both economically and environmentally
sound ways. Conversely, regulatory agencies can do their part by
imposing regulations based on accurate scientific information, not the
prevailing political pressures. Mutual education between regulators, the
petroleum industry, and the public at all levels is an important step
n environmentallyresponsible, costeffective operations.
This partnership requires cooperation, teamwork, commitment,
credibility, and trust among all parties involved in the exploration for
and production of oil, including operating company managers, engi
neers, geologists, contractors, subcontractors, work crews, regulators,
courts, and legislators. Environmentally related activities must
be oriented toward improved environmental awareness and protection,
not the avoidance of responsibility for environmental protec
ion. Environmental awareness must be an integral part of everyone's
daily job.
This type of attitude toward environmental responsibility has been
formally adopted as a set of principles by the American Petroleum
Institute member companies. These principles are known as the Guidng Principles for Environmentally Responsible Petroleum Operations,
Introduction to Environmental Control in the Petroleum Industry
15
Guiding Principles for Environmentally
Responsible Petroleum Operations
Recognize and respond to community concerns about raw materials,
products, and operations.
Operate plants and facilities and handle raw materials and products in a
manner that protects the environment and the safety and health of
employees and the public.
Make safety, health, and environmental considerations a priority in
planning and development of new products and processes.
Advise promptly appropriate officials, employees, customers, and the
public of information of significant industry related safety, health, and
environmental hazards and recommend protective measures.
Counsel customers, transporters, and others in the safe use, transportation,
and disposal of raw materials, products, and waste materials.
Economically develop and produce natural resources and conserve those
resources by using energy efficiency.
Extend knowledge of conducting or supporting research on the safety,
health, and environmental effects of raw materials, products, processes,
and waste materials.
Reduce overall emissions and waste generation.
Work with others to resolve problems created in disposal of hazardous
substances from operations.
Participate with government and others in creating responsible laws, regulations,
and standards to safeguard the community, workplace, and environment.
Promote these principles and practices by sharing experiences and offering
assistance to others who produce, handle, use, transport, or dispose of
similar raw materials, petroleum products, and wastes.
Source: American Petroleum Institute, 1992. Reprinted by permission of the American
Petroleum Institute,
The benefits of being proactive in protecting the environment, as
opposed to simply reacting to legislative, regulatory, or courtordered
mandates, can actually lower the longterm costs of doing business.
For example, voluntary waste reduction and site remediation activities
could result in the cleanup of a site at costs up to six times lower
16
Environmental Control in Petroleum Engineering
han if a regulatory agency mandates the cleanup, even if the identical
emediation methods and standards are used (Knowles, 1992).
REFERENCES
American Petroleum Institute, "Oil and Gas Industry Exploration and Produc
tion Wastes," API Publication 4710109, Washington, D.C., July 1987,
American Petroleum Institute, "API Environmental Guidance Document:
Onshore Solid Waste Management in Exploration and Production Opera
tions," Washington, D.C., Jan. 1989.
American Petroleum Institute, "RP9000, Management Practices: SelfAssess
ment Process, and Resource Materials," Washington, D.C., Dec. 1992,
American Petroleum Institute, Basic Petroleum Data Handbook, Vol. 13, No.
3, Washington, D.C., Sept. 1993.
Bleier, R., Leuterman, A. J. J., and Stark, C., "Drilling Fluids Making Peace
with the Environment," J, Pet. Tech., Jan. 1993, pp. 610.
Derkies, D. L. and Souders, S. H., "Pollution Prevention and Waste Minimiz
ation Opportunities for Exploration and Production Operations," paper SPE
25934 presented at the Society of Petroleum Engineers/Environmental
Protection Agency's Exploration and Production Environmental Conference,
San Antonio, TX, March 710, 1993.
Deuel, L. E., "Evaluation of Limiting Constituents Suggested for Land
Disposal of Exploration and Production Wastes," Proceedings of the U.S.
Environmental Protection Agency's First International Symposium on Oil
and Gas Exploration and Production Waste Management Practices, New
Orleans, LA, Sept. 1013, 1990, pp. 411430.
Gilliland, A., Environmental Reference Manual for the Oil and Gas Exploration and Producing Industry, Texas Independent Producers and Royalty
Owners Association, Austin, TX, 1993.
Godec, M. L. and Biglarbigi, K., "Economic Effects of Environmental
Regulations of Finding and Developing Crude Oil in the U.S.," J. Pet.
Tech., Jan. 1991, pp. 7279.
Gray, P. R,, "NORM Contamination in the Petroleum Industry," J. Pet. Tech.,
Jan. 1993, pp. 1216.
Guckian, W. M., Hurst, K. G., Kerns, B. K., Moore, D. W., Siblo, J. T., and
Thompson, R. D., "Initiating an Audit Program: A Case History," paper
SPE 25955 presented at the Society of Petroleum Engineers/Environmental
Protection Agency's Exploration and Production Environmental Conference,
San Antonio, TX, March 710, 1993.
Hudgins, C. M., Jr., "Chemical Treatments and Usage in Offshore Oil and
Gas Production Systems," /. Pet. Tech., May 1992, pp. 604611.
introduction to Environmental Control in the Petroleum Industry
17
Interstate Oil Compact Commission, EPA/IOCC Study of State Regulation of
Oil and Gas Exploration and Production Waste, Interstate Oil Compact
Commission, Oklahoma City, OK, Dec. 1990.
Knowles, C. R., "A Responsible Remediation Strategy," Proceedings of Petro
Safe '92, Houston, TX, 1992.
Mount, D. R., Gulley, D. D., and Evans, J. M., "Salinity/Toxicity Relation
ships to Predict the Acute Toxicity of Produced Waters to Freshwater
Organisms," paper SPE 26007 presented at the Society of Petroleum
Engineers/Environmental Protection Agency's Exploration and Production
Environmental Conference, San Antonio, TX, March 710, 1993.
National Research Council, Oil in the Sea: Inputs, Fates, and Effects,
Washington, D.C.: National Academy Press, 1985.
Perkins, J., "Cost to Petroleum Industry of Major New and Future Federal
Government Environmental Regulations," American Petroleum Institute,
Discussion Paper #070, Oct. 1991.
Perry, C. W, and Gigliello, K., "EPA Perspective on Current RCRA Enforce
ment Trends and Their Application to Oil and Gas Production Wastes,"
Proceedings of the U.S. Environmental Protection Agency's First Inter
national Symposium on Oil and Gas Exploration and Production Waste
Management Practices, New Orleans, LA, Sept. 1013, 1990, pp. 307318,
Savage, L. L., "Even If You're On the Right Track, You'll Get Run Over If
You Just Sit There: Source Reduction and Recycling in the Oil Field,"
paper SPE 26009 presented at the Society of Petroleum Engineers/Environ
mental Protection Agency's Exploration and Production Environmental
Conference, San Antonio, TX, March 710, 1993.
Snavely, E. S., "Radionuclides in Produced Water," report prepared for
the API Guidelines Steering Committee, American Petroleum Institute,
Washington, D.C., 1989.
Stephenson, M. T., "Components of Produced Water: A Compilation of
Industry Studies," J. Pet. Tech., May 1992, pp. 548603.
Stilwell, C. T., "Area WasteManagement Plans for Drilling and Production
Operations," /. Pet. Tech., Jan. 1991, pp. 6771.
Sullivan, M. J., "Evaluation of Environmental and Human Risk from Crude
Oil Contamination," J. Pet. Tech., Jan. 1991, pp. 1416.
Thurber, N. E., "Waste Minimization for LandBased Drilling Operations,"
./. Pet. Tech., May 1992, pp. 542547.
Wojtanowicz, A. K., Field, S. D., and Osterman, M. C., "Comparison Study
of Solid/Liquid Separation Techniques for Oilfield Pit Closures," J. Pet.
Tech,, July 1987, pp. 845856.
CHAPTER 2
Drilling and
Production Operations
In the upstream petroleum industry, there are two major operations that
can potentially impact the environment: drilling and production. Both
operations generate a significant volume of wastes. Environmentally
esponsible actions require an understanding of these wastes and how they
are generated. From this understanding, improved operations that minimize
or eliminate any adverse environmental impacts can be developed.
Drilling is the process in which a hole is made in the ground to
allow subsurface hydrocarbons to flow to the surface. The wastes
generated during drilling are the rock removed to make the hole (as
cuttings), the fluid used to lift the cuttings, and various materials added
o the fluid to change its properties to make it more suitable for use
and to condition the hole.
Production is the process by which hydrocarbons flow to the surface
o be treated and used. Water is often produced with hydrocarbons and
contains a variety of contaminants. These contaminants include dis
solved and suspended hydrocarbons and other organic materials, as
well as dissolved and suspended solids. A variety of chemicals are also
used during production to ensure efficient operations.
During both drilling and production activities, a variety of air
pollutants are emitted. The primary source of air pollutants are the
emissions from internal combustion engines, with lesser amounts from
other operations, fugitive emissions, and site remediation activities.
2.1 DRILLING
The process of drilling oil and gas wells generates a variety of
different types of wastes. Some of these wastes are natural byproducts
18
Drilling and Production Operations
19
of drilling through the earth, e.g., drill cuttings, and some come from
materials used to drill the well, e.g., drilling fluid and its associated
additives. This section reviews the drilling process, the drilling fluid
composition, methods to separate cuttings from the drilling fluid, the
use of reserves pits, and site preparation,
2.1.1
Overview of the Drilling Process
Most oil and gas wells are drilled by pushing a drill bit against the
rock and rotating it until the rock wears away. A drilling rig and
system is designed to control how the drill bit pushes against the rock,
how the resulting cuttings are removed from the well by the drilling
fluid, and how the cuttings are then removed from the drilling fluid
so the fluid can be reused.
The major way in which drilling activities can impact the environ
ment is through the drill cuttings and the drill fluid used to lift the
cuttings from the well. Secondary impacts can occur due to air emis
sions from the internal combustion engines used to power the drill
ing rig.
During drilling, fluid is injected down the drill string and though
small holes in the drill bit. The drill bit and holes are designed to allow
the fluid to clean the cuttings away from the bit. The fluid, with
suspended cuttings, then flows back to the surface in the annulus
between the drill string and formation. At the surface, the cuttings are
separated from the fluid; the cuttings, with some retained fluid, are
then placed in pits for later treatment and disposal. The separated fluid
is then reinjected down the drill string to lift more cuttings.
The base fluid most commonly used in the drilling process is water,
followed by oil, air, natural gas, and foam. When a liquid is used as
the base fluid, either oilbased or waterbased, it is called "mud."
Waterbased drilling fluids are used in about 85% of the wells drilled
worldwide. Oilbased fluids are used for virtually all of the remain
ing wells.
During the drilling process, some mud can be lost to permeable
underground formations. To ensure that mud is always available to
keep the well full, extra mud is always mixed at the surface and
kept in reserves or mud pits for immediate use. Reserves pits vary in
size, depending on the depth of the well. The pits can be up to an
acre in area and be 510 feet deep. Steel tanks are also used for mud
20
Environmental Control in Petroleum Engineering
pits, especially in offshore operations. Pits are also used to store
supplies of water, waste fluids, formation cuttings, rigwash, and
rainwater runoff.
2.1.2
Drilling Fluids
Drilling fluids serve a number of purposes in drilling a well. In most
cases, however, the base fluid does not have the proper physical or
chemical properties to fulfull those purposes, and additives are required
to alter its properties. The primary purpose of drilling fluid is to
remove the cuttings from the hole as they are generated by the bit
and carry them to the surface. Because solids are more dense than the
fluid, they will tend to settle downward as they are carried up the
annulus. Additives to increase the fluid viscosity are commonly used
to lower the settling velocity.
Drilling fluids also help control the well and prevent blowouts.
Blowouts occur when the fluid pressure in the wellbore is lower than
he fluid pressure in the formation. Fluid in the formation then flows
nto the wellbore and up to the surface. If surface facilities are unable
to handle this flow, uncontrolled production can occur. The primary
fluid property required to control the well is the fluid's density,
Additives to increase fluid density are commonly used.
Drilling fluids also keep the newly drilled well from collapsing
before steel casing can be installed and cemented in the hole. The
pressure of the fluid against the side of the formation inhibits the walls
of the formation from caving in and filling the hole. Additives are
often used to prevent the formation from reacting with the base fluid.
One common type of reaction is shale swelling.
A final function of drilling fluids is to cool and lubricate the drill
bit as it cuts the rock and lubricate the drill string as it spins against
he formation. This extends the life of the drill bit and reduces the
orque required at the rotary table to rotate the bit. Additives to
ncrease the lubricity oT the drilling fluid are commonly used, particu
arly in highly deviated or horizontal wells.
Many of the additives used in drilling fluids can be toxic and are
now regulated. To comply with new regulations, many new additives
have been formulated (Clark, 1994), These new additives have a lower
oxicity than those traditionally used, thus lowering the potential for
environmental impact.
Drilling and Production Operations
21
Water-based Drilling Fluids
Water is the most commonly used base for drilling fluids or muds.
Because it does not have the physical and chemical properties needed
to fulfill all of the requirements of a drilling mud, a number of additives
are used to alter its properties. During drilling, formation materials get
incorporated into the drilling fluid, further altering its composition and
properties. A typical elemental composition of common constituents
of waterbased drilling muds is given in Table 21 (Deeley, 1990).
These constituents are discussed in more detail below.
Viscosity Control
One of the most important functions of a drilling fluid is to lift
cuttings from the bottom of the well to the surface where they can be
removed. Because cuttings are more dense than water, they will settle
downward through the water from gravitational forces. The settling
velocity is controlled primarily by the viscosity of the water and the
size of the cuttings. Because the viscosity of water is relatively low,
the settling velocity for most cuttings is high. To remove the cuttings
from the well using water only, a very high water velocity would be
required. To lower the settling velocity of cuttings and decrease the
corresponding mud circulation rate, viscosifiers are added to the water
to increase its viscosity.
The most commonly used viscosifier is a hydratable clay. Some
clays, like smectite, consist of molecular sheets with loosely held
cations between them, such as Na+. If the clay is contacted with water
having a cation concentration that is lower than the equilibrium
concentration for the cation in the clay, the cation atom between the
sheets can be exchanged with water molecules. Because water mole
cules are physically larger than most cations, the spacing between the
clay sheets expands and the clay swells (hydrates). During the mixing
and shearing that occurs as water is circulated through the well, these
clay sheets can separate, forming a suspension of very small solid
particles in the water. The viscosity of this suspension is significantly
higher than that of pure water and is more effective in lifting the larger
formation cuttings out of the well.
The most common clay used is Wyoming bentonite. This clay
is composed mostly of sodium montmorillonite, a variety of smectite.
Table 2-1
Elemental Composition of Drilling Fluid Constituents (mg/kg)
Water
Cuttings
Barite
Clay
Chromelignosulfonate
Lignite
Caustic
Aluminum
Arsenic
Barium
Calcium
Cadmium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Mercury
Nickel
Potassium
Silicon
Sodium
Strontium
0.3
0.0005
0.01
15
0.0001
0.001
0.0002
0.003
0.5
0.003
4
0.0001
0.0005
2.2
7
6
0.07
40,400
3.9
158
240,000
0.08
183
2.9
22
21,900
37
23,300
0.12
15
13,500
206,000
3,040
312
40,400
34
590,000
7,900
6
183
3.8
49
12,950
685
3,900
4.1
3
660
70,200
3,040
540
88,600
3.9
640
4,700
0.5
8.02
2.9
8.18
37,500
27.1
69,800
0.12
15
2,400
271,000
11,000
60.5
6,700
10.1
230
16,100
0.2
40,030
5
22.9
7,220
5.4
5,040
0.2
11.6
3,000
2,390
71,000
1030
6,700
10.1
230
16,100
0.2
65.3
5
22.9
7,220
5.4
5,040
0.2
11.6
460
2,390
2,400
1030
0.013
0.039
0.26
5,400
0.0013
0.00066
0.00053
0.039
0.04
0.004
17,800
5
0.09
51,400
339
500,000
105
Source: Deeley, 1990.
jnmentai
Element
O
s
**•*
i.
S"
I?
si
55
2
3
S'
fls
_S'
Drilling and Production Operations
23
Most drilling fluids are composed of 3% to 7% bentonite by volume.
Other clays can be used, but typically do not provide as high a mud
viscosity for the same amount of clay added. During normal drilling
operations, natural clays in the formations can also be incorporated
into the mud, increasing the clay content and mud viscosity over time.
Adding hydratable clays to the water used as a drilling fluid pro
vides a second important benefit for drilling of wells. Because the
pressure of the mud in the wellbore is normally kept above the
pressure in the formation to prevent blowouts, the water (mud filtrate)
will flow into a permeable formation and be lost. When this occurs,
the suspended clays are filtered out at the face of the formation,
building a mudcake along the walls of the well. The clay particles of
this mudcake are virtually always smaller than the grains of a perme
able formation, so the resulting permeability of the mudcake is much
lower than that of the formation. This low permeability mudcake acts
as a barrier to minimize subsequent fluid losses to the formation.
Because fluid losses are lower, the total volume of mud needed to drill
the well is reduced.
One difficulty with using clay particles for viscosity control is that
they tend to flocculate (agglomerate) if the mud is allowed to remain
static in the wellbore. When flocculation occurs, the mud viscosity can
significantly increase. If the viscosity becomes too high, the mud can
become too difficult to pump at reasonable pressures and flow rates,
rendering it ineffective as a drilling fluid. Flocculation occurs when
the electrostatic charges along the periphery of the clay particles are
allowed to attract other clay particles. The flocculation rate increases
with an increasing clay content and electrolyte (salt) concentration in
the mud.
A variety of materials are available that can suppress flocculation
of clay particles in drilling muds, although none are totally effective
under all conditions. The most common deflocculants are phosphates,
tannins, lignites, and lignosulfonates. Phosphate deflocculants can be
used when the salt concentrations and temperatures are low. Tannins
are effective in moderate concentrations of electrolyte concentration
and moderate temperatures. Lignites and lignosulfonates can be effec
tive at high temperatures, particularly if they are complexed with heavy
metals like chromium.
Polymers, like xanthan gum, have also been developed to increase
the viscosity of drilling mud. These polymers have the advantage of
4
Environmental Control in Petroleum Engineering
hear thinning, which lowers the viscosity and required pumping power
uring high pumping rates, when a high viscosity is not needed,
Density Control
Another important function of a drilling fluid is to control the fluid
ressure in the wellbore. Because many formations are hydrostatically
ressured or overpressured and the pressure in the wellbore must be
ept higher than that in the formation, the pressure in the wellbore
must normally be higher than the hydrostatic pressure for pure water
o prevent the well from blowing out. The fluid pressure in the
wellbore is controlled by varying the density of the drilling fluid. The
ensity is varied by adding heavy solids to the fluid.
Although the clays added to control the fluid viscosity also increase
he fluid density, their specific gravity of 2.6 and low concentration
n the mud is insufficient to provide the needed density for many
pplications. Materials having a higher specific gravity are normally
equired to obtain the desired mud density.
The most common material used to increase the density of drilling
mud is barite (barium sulfate, BaSO4). Barite has a high specific
ravity of 4.2. In some wells requiring a very high density, barite can
onstitute as much as 35% of the drilling fluid by volume. Because
f the high specific gravity of barite, viscosity control additives (clays)
re normally used to keep the barite suspended in the fluid.
Other materials that can be used to control drilling fluid density
nclude calcium carbonate, iron carbonate, ilmenite (FeO–TiO2) and
ematite (Fe2O3). These materials are harder than barite and are less
usceptible to particle size reduction during drilling. Although these
materials have a lower specific gravity than barite, they have the added
enefit of lowering the barium concentration in the drilling rnud,
Galena (PbS) can also be used, but will result in lead being added to
he drilling mud. Rarely, barium carbonate has been used.
Lost Circulation Control
During drilling, fluid is lost to the formation as drilling fluid leaks
nto permeable strata. To minimize this loss, small particles are added
o drilling fluids that will filter out on the formation face as fluid is
ost. These solids then form a low permeability mudcake that limits
Drilling and Production Operations
25
further fluid loss. In most cases, the clay particles added to control
the viscosity of a drilling fluid are successful in controlling fluid loss
to the formation.
In some formations, however, the pore sizes may be so large that
the clay particles are unable to bridge the pores and build a filter cake.
Such formations may include those having natural or induced fractures,
very high permeability sands, or vugs. To limit fluid loss in such
formations, larger solids can be added to the drilling fluid, A mudcake
of clay particles is then built on the bridge created by those solids,
Solids that are commonly used for this application include mica, cane
fibers, ground nutshells, plastic, sulfur, perlite, cellophane, cottonseed
hulls, and sawdust.
If solids cannot be used to build a filter cake, the viscosity of the
drilling fluid can be increased to limit fluid loss. Watersoluble poly
mers like starch, sodium polyacrylate, and sodium carboxymethyl
cellulose can be used.
A high mud pH between 9.5 and 10.5 is almost always desired in
drilling operations. A high pH suppresses the corrosion rate of drilling
equipment, minimizes hydrogen embrittlement of steel if hydrogen
sulfide enters the mud, lowers the solubility of calcium and magnesium
to minimize their dissolution, and increases the solubility of ligno
sulfonate and lignite additives. A high pH is also beneficial for many
new organic viscosity control additives. To keep the pH in the desired
range, caustic (sodium hydroxide) is normally added to the mud. Some
of the new polymer muds, however, have better shale stabilization
properties at a lower pH (Clark, 1994).
Lubricants
During drilling, a considerable amount of friction can be generated
between the drill bit and formation and between the drill string and
wellbore walls, particularly for deviated and horizontal wells. To
reduce this friction, lubricants are sometimes added to drilling fluids.
These lubricants speed drilling and help maintain the integrity of the
well. Common lubricants include diesel oil, mineral/vegetable oils,
glass beads, plastic beads, wool grease, graphite, esthers, and glycerols.
26
Environmental Control in Petroleum Engineering
If a drill string becomes stuck in a well, a lubricant is usually
circulated through the well to help free it. These spotting fluids have
traditionally been formulated with diesel or mineral oils. Because these
fluids "contaminate" cuttings with a hydrocarbon, the discharge and
disposal options for cuttings is limited in some areas. Waterbased
spotting fluids are also available (Clark and Almquist, 1992).
Corrosion Inhibitors
Corrosion is commonly caused by dissolved gases in the drilling
mud, e.g., oxygen, carbon dioxide, or hydrogen sulfide. Optimum
corrosion protection of drilling equipment would include elimination
of these gases from the mud. If elimination is not possible, the
corrosion rate should be reduced. A wide variety of chemicals are
available to inhibit corrosion from drilling mud. These additives are
often used even when the pH is maintained in the desired range.
Corrosion inhibitors do not prevent corrosion, but reduce the cor
rosion rate to acceptable levels, e.g., below 400 mills per year or
0.02 Ibm metal per ft2 of metal in 10 hours. Inhibitors coat the metal
surface and limit the diffusion rate of corrosive chemicals to the
surface. The most common inhibitors utilize a surfactant that protects
the metal with a coating of oil. High molecular weight morpholines
and filming amines are most commonly used for oilfield applications,
Ethylene diamine tetracetic acid (EDTA) is sometimes used to dissolve
pipe corrosion.
Oilsoluble organic inhibitors applied every 10 hours appear to
successfully reduce oxygen corrosion. These inhibitors are strongly
absorbed on clays and cuttings, however, increasing the amount of
inhibitor required. Watersoluble organic corrosion inhibitors may not
be effective for controlling oxygen corrosion, although they can be
used to reduce pitting from H2S in the absence of oxygen. A more
complete discussion of corrosion is given by Jones (1988).
Biocides
Sulfur reducing bacteria can grow in many drilling muds, particu
larly those containing starches and polymer additives. These bacteria
can degrade the mud and can enter the formation, where they can sour
the reservoir (generate hydrogen sulfide gas). Hydrogen sulfide causes
Drilling and Production Operations
27
corrosion of equipment when present in drilling muds. To prevent these
bacteria from growing, biocides are added to drilling fluids. Common
biocides include paraformaldehyde, chlorinated phenol, isothiazolin,
and glutaraldehyde. The latter two biocides have lower toxicities and
are replacing the former two in popularity (Clark, 1994).
Formation Damage Control
Many formations contain active clays that swell upon contact with
fresh water. These swelling clays can plug pores in the reservoir,
lowering its permeability, or they can cause shale around the wellbore
to slough into the wellbore, "wellbore washout." To prevent these
reactions from occurring, salts are commonly added to the drilling
fluid. These salts prevent water molecules from exchanging with the
cations in the clays. Salts commonly used include sodium and potas
sium chloride. Potassium acetate or potassium carbonate can also be
used, as well as cationic polymers. Shale stabilization additives based
on glycols have also been successfully used (Reid et al., 1993). A
number of cationic polymer muds having good shale stabilization
properties have also been introduced (Clark, 1994).
A related problem during drilling is that cuttings can ball around
the bit, forming a gummy paste. This paste reduces drilling speed
because it is not easily removed from the bit by the drilling fluid.
Copolymer/polyglycol muds have been successfully used to prevent
bitballing (Enright and Smith, 1991).
If a well is drilled through a salt dome, a waterbased mud that is
saturated in chloride salts may be required to prevent excessive
dissolution of the salt along the wellbore.
Oil-based Drilling Fluids
Various organic fluids are also used as a base for drilling muds. In
some cases, the properties of these "oilbased" muds are superior to
those of waterbased muds. Like water, however, these organic fluids
do not have all of the proper physical and chemical properties needed
to fulfill all of the requirements of a drilling mud, so various additives
are also used.
Oilbased muds are often preferred for hightemperature wells, i.e.,
wells with temperatures greater than about 300°F. At temperatures
28
Environmental Control in Petroleum Engineering
above that level, many of the additives used with a waterbased fluid
can break down.
Oilbased muds are also used in wells containing watersensitive
minerals, e.g., salt, anhydrite, potash, gypsum, or hydratable clays and
shales. Using an oilbased mud in a reactive formation can reduce
wellbore washout by more than 20% (Thurber, 1990). Reducing the
amount of washout reduces both the volume of drill cuttings to be
disposed of and the volume of drilling fluid required to drill the hole.
Reducing interactions between the drilling fluid and formation minerals
by using an oilbased mud also limits the degradation of cuttings into
smaller particles, which improves the efficiency of separating the
solids from the drilling fluid.
Oilbased muds are also used in wells containing reactive gases like
CO2
H2S. When oilbased muds are used, corrosion is minimized
because the continuous oil phase does not act as an electrolyte. These
gases are prime contributors to corrosion of drilling equipment in
waterbased mud systems.
Another application of oilbased muds is in wells requiring unusu
ally high levels of lubrication between the drill pipe and the formation.
These wells include deviated or horizontal wells, where the drill pipe
rotates against the formation over long intervals. Oilbased muds are
also useful for freeing pipe that has become stuck in the well.
Oilbased muds are generally more expensive than waterbased
muds and have a greater potential for adverse environmental impact.
The benefits of oilbased muds, however, can result in a significant
savings in the cost of drilling a well. Because of their superior
properties, drilling can often be completed faster, which may result
in lower overall environmental consequences than those of waterbased
muds. Because oilbased muds are more expensive, they are also more
likely to be reconditioned and reused than waterbased muds.
Historically, the most common base oil used has been # 2 diesel. It
has an acceptable viscosity, low flammability, and a low solvency for
any rubber in the drilling system. Diesel, however, is relatively toxic,
making the environmental impact of dieselbased muds generally
higher than those of waterbased muds.
The most common additive used in oilbased muds for viscosity
control is water in the form of a waterinoil emulsion. Small, dis
persed drops of water in the continuous oil phase can significantly
increase the mud viscosity. Water contents of typically 10% have been
Drilling and Production Operations
2S
used. A chemical emulsifier (surfactant) is normally added to prevent
he water droplets from coalescing and settling from gravitational
forces. Commonly used emulsifiers are calcium or magnesium fatty
acid soaps. If further viscosity increases are required, solids can be
added to the mud, including asphalts, aminetreated bentonite, calcium
carbonate, or barite.
The density of oil is significantly lower than that of water, so den
sity control additives normally must be used. The water in waterinoii
emulsions only slightly increases the mud density, so solids are norm
ally added. The same solids that are used to increase the viscosity
asphalts, aminetreated bentonite, calcium carbonate, or barite—can be
used to increase the density. One limitation with oilbased muds is that
most of the solids that enter the mud, including cuttings, are water
wet. To prevent the solids from concentrating in the dispersed water
droplets and settling out, chemical wettability agents (surfactants) are
added to change the wettability of the solids to oilwet. This allows
he solids to be dispersed through the more voluminous oil phase.
One of the advantages of oilbased muds is their compatibility with
watersensitive formations. Because the continuous phase is oil, only
oil can enter the formation as a filtrate. Water invasion is severely
imited, which minimizes the damage to the formation. Because clay
particles do not flocculate in oilbased muds, bitballing is also
minimized. If fluid loss becomes too high, fluid loss agents like
bentonite, asphalt, polymers, manganese oxide, and aminetreated
ignite can be used.
Although oilbased muds have a lower corrosion rate than waterbased
muds, corrosion can occur, particularly when drilling through a formation
containing CO2 or H2S. Like waterbased muds, the primary method to
control corrosion is to control the pH of the water phase of the mud. A
common additive for pH control of oilbased muds is calcium oxide.
A number of oilbased muds using organic materials have been
developed as lowtoxicity substitutes for diesel (Friedheim and Shinnie,
1991; Peresich et al. 1991). Mineral and synthetic oils are becoming
ncreasingly popular as a base for drilling mud (Clark, 1994).
Unwanted Components
All drilling muds generally have a number of unwanted components
hat can potentially harm the environment. The most common of these
30
Environmental Control in Petroleum Engineering
are heavy metals, salt, and hydrocarbons. The concentration of these
materials varies significantly. The primary concern arises when the
drilling fluid must be disposed of.
Heavy Metals
Heavy metals can enter drilling fluids in two ways: Many metals are
naturally occurring in most formations and will be incorporated into the
fluid during drilling; other metals are added to the drilling fluid as part
of the additives used to alter the fluid properties. The most commonly
found metals have traditionally been barium from barite weighting agents
and chromium from chromelignosulfonate deflocculants.
Heavy metals naturally occur in most rocks and soils, although at
relatively low concentrations. The elemental concentrations of native soils
and gravels on the Alaskan North Slope are summarized in Table 22,
Although the concentrations of the major elements will vary from car
bonate to siliceous rocks, the concentration of the trace elements, including
heavy metals, is probably representative of rocks and soils of many other
areas. Naturally occurring metals of particular concern include arsenic,
barium, cadmium, chromium, lead, and mercury.
Drilling fluids typically contain high concentrations of barium.
Barium is a constituent of barite, which is used as a density control
material. The most commonly used form of barium, however, is barium
sulfate, which is highly insoluble. Because of its low solubility, it will
not leach with groundwater movement, nor will it be taken up by
plants and enter the food chain.
Chromium is another major constituent of many mud additives,
particularly chromebased deflocculants. Chromium in its toxic hexava
lent form can be used as a gel inhibitor/thinner, a hightemperature
stabilizer, a dispersant, a biocide, and a corrosion inhibitor. It is
believed, however, that hexavalent chromium is quickly reduced to its
relatively nontoxic trivalent form in a mud system (Campbell and
Akers, 1990). Typical chromium levels in drilling muds are between
100 and 1,000 mg/L (Bleier, Leuterman, and Stark, 1993).
Another significant source of heavy metals in drilling fluid is the
hread compound (pipe dope) used on the pipe threads when making
up a drill string. Pipe dope serves two primary purposes: (1) it prevents
the seizure of the joint from galling at high stresses and (2) it seals
the joint and prevents fluid flow along the threads. Early formulations
Drilling and Production Operations
31
Table 2-2
Composition of Alaskan North Slope Soils and Gravels
Element
Aluminum
Arsenic
Barium
Boron
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Nickel
Potassium
Selenium
Silicon
Silver
Sodium
Strontium
Vanadium
Zinc
Mean Level
{mg/kg dry)
Standard Deviation
7,050
1.83
6,180
2.15
397
802
29.4
0.153
46,700
27,4
0,185
65,500
11
14
16
19,600
4.24
3,440
484
0.268
21.3
11.9
15,800
5.06
3,880
1,040
0.289
14.8
699
810
0.267
1,640
0.26
0.187
6,230
0.177
529
672
140
140
93.4
29.9
74.6
46.1
Source: from Schumacher et al, 1991.
Copyright SPE, with permission.
of pipe dope contained as much as 60% metals by weight, primarily
ead, zinc, copper, or combinations of these metals (McDonald, 1993).
These metals are malleable and deform within the threads without
fracturing, forming both a seal and lubricant for the threads. These
metals, however, can leach out of the pipe dope and contaminate the
drilling fluid, particularly if an excess of pipe dope is used.
Another source of heavy metals in drilling fluid is from crude oil.
Crude oil naturally contains widely varying concentrations of various
32
Environmental Control in Petroleum Engineering
heavy metals. These metals can enter the drilling fluid during drilling
through a formation containing crude oil or if a kick occurs and oil
flows into the well. Metals found in crude oil include aluminum,
boron, calcium, chromium, cobalt, copper, gold, iron, lead, magnesium,
manganese, nickel, phosphorus, platinum, silicon, silver, sodium,
strontium, tin, uranium, and vanadium. Of these elements, vanadium
and nickel occur in the highest concentrations. The concentration of
metals in some crude oils is typically on the order of a few parts per
million to a few tens of parts per million, although concentrations as
high as thousands of parts per million have been reported (National
Research Council, 1985).
A number of other metals are found in drilling fluid additives,
although at lower concentrations. Arsenic can be used as a biocide to
prevent the growth of bacteria. Cadmium is found in some pipe dopes,
The mineral barite, the source for the barium sulfate used for density
control, can have relatively high naturally occurring levels of cadmium
and mercury (Candler et al., 1990). Mercury has also been used in
manometers in the natural gas industry to meter the flow rate of gas,
Zinc is occasionally used as inorganic zinc salts for density control
or as hydrogen sulfide scavengers to minimize corrosion and maintain
human safety.
Another unwanted component of drilling fluid at disposal time are
salts. Salts, like sodium or potassium chloride, are often added to
drilling fluid to protect sensitive formations from reacting with the
drilling fluid. The salt concentration of a drilling fluid can also
significantly increase if a well is drilled through a salt dome or a
formation having water with a high salt concentration.
Hydrocarbons
Except for oilbased muds, hydrocarbons are normally an undesir
able material in drilling rnud because they contaminate the cuttings.
Hydrocarbons enter a mud while drilling through a hydrocarbon
bearing formation or when oil is used for a spotting fluid when a pipe
becomes stuck. In general, the deeper the well, the greater the concen
tration of hydrocarbons that enter the mud.
Drilling and Production Operations
33
2.1.3 Drilling Fluid Separations
During the drilling process, a large volume of cuttings are generated
and carried out of the well by the drilling fluid. These cuttings must
be separated from the mud liquid so the liquid can be reinjected into
the drill string to remove more cuttings. Cuttings contaminated with
drilling mud are a major source of petroleum industry waste. The
potential environmental impact of such cuttings can be significantly
reduced by separating the solid cuttings from the more toxic mud,
The effectiveness of separating cuttings from the mud depends
primarily on the cuttings size. Separations can be enhanced if the
cuttings size is kept as large as possible. Cuttings size depends on a
number of factors. The most important factor in keeping cuttings size
large is to generate large cuttings at the bit during drilling. The initial
cuttings size is controlled by the bit type, the weight on bit, and the
formation type. A second factor in controlling the cuttings size is to
minimize additional grinding of the cuttings in the well as they are
lifted to the surface. Cuttings removal is controlled by the hydraulic
design of the bit jets, the mud viscosity, the mud velocity, the well
depth, the rotational speed of the drill string, and the mechanical
strength of the cuttings. A third factor controlling cuttings size is
whether the cuttings contain clays which can hydrate (deflocculate)
in the mud before separation. Clay hydration can be controlled by the
mud chemistry. Additives like polyacrylamides, polymers and salts, as
well as oilbased muds, can help control formation reactivity and
minimize degradation of solids.
The first stage of separation is to remove large cuttings from the
mud with a shale shaker. Shale shakers are vibrating screens over
which the mud passes. The liquid and small cuttings pass through the
screens, while the larger cuttings remain on the screen. If the mud
contains gas, the shale shaker will also separate much of it from the
mud. The mud and small cuttings that pass through the screens are
returned to the mud pit, where additional separation of cuttings and
gases occurs from gravitational settling. The effectiveness of vibrating
screens depends on the vibrator placement, vibration frequency, vibra
tion amplitude, speed of solids as they pass across the screens, and
screen opening size (Hoberock, 1980; Lai and Hoberock, 1988).
Chemicals can be added to the mud that cause the small clay
particles to coagulate or flocculate into larger groups of particles
34
Environmental Control in Petroleum Engineering
(American Petroleum Institute, 1990b). The larger flocculates then
settle more rapidly in the mud pits. This process involves the neu
tralization of the surface charge (zeta potential) on suspended par
ticles to overcome coulombic electrical repulsion between the par
ticles and allow aggregates to form. Inducing alternating electrical
currents to overcome the coulombic repulsion has also been proposed
(Farrell, 1991).
If a drilling mud contains gas that is not removed by the solids
separation equipment, a vacuum chamber can be added to the mud
system. This lowers the mud pressure in the chamber and expands the
size of the gas bubbles, allowing them to be separated from the liquid
by gravity more rapidly. In these systems, the mud is typically passed
over inclined planes in thin layers to enhance separation.
If the proper equipment and procedures are not used to remove the
cuttings as they are added to the mud system, the concentration of
cuttings in the mud gradually increases with time, and the mud
properties, such as density and viscosity, are degraded. The maxi
mum tolerable solids concentration varies with the mud used, but is
generally between 4% and 15% (Wojtanowicz, 1991). To maintain the
mud properties in the desirable range, the mud can be diluted; this
requires the addition of more base fluid, either water or oil, and many
of the chemicals needed to alter its chemical properties. Dilution,
however, increases the volume of drilling waste that must ultimately
be disposed of.
In many cases, shale shakers and settling pits are insufficient to
separate the mud solids from liquids, and further treatment with
advanced technology is required. For example, after separating the
solids from the mud, a significant volume of liquid is normally
retained with the cuttings. Volumetric measurements from offshore
platforms have shown that the total volume of liquids with the cuttings
after discharge can be from 53% to 73% (Wojtanowicz, 1991). In some
cases, further dewatering of the solids may be required before disposal.
Advanced separation methods are discussed in Chapter 6.
One difficulty with using advanced technology for improved separa
tions at a drill site is the high cost of equipment rental. The expendi
ure for this equipment can be easier to justify if a good economic
model for their benefits is used. One such model has been proposed
by Lai (1988) and was subsequently verified by field performance (Lai
and Thurber, 1989).
2,1.4
Drilling and Production Operations
3S
Reserves Pits
The most common method for the disposal of drilling wastes for
onshore wells is in onsite reserves pits. The contents of reserves pits vary,
depending on the drilling mud and the types of formations drilled.
Reserves pits, however, can cause local environmental impact, particu
larly older pits that contain materials that are currently banned from
such disposal or that were not constructed according to current regula
tions. The environmental impact of modern reserves pits are minimal.
The composition of the fluid in a reserves pit may be different from
that of the original drilling fluid. Chemical and physical alterations
of drilling fluids can occur during and after drilling from the heat and
pressure encountered during drilling or from the addition of formation
materials. Other materials may also be added to the pit before closure,
either deliberately or inadvertently. Such materials include caustic
soda, rig wash, diesel fuel, waste oil from machinery, metal and plastic
containers, and other refuse (Powter, 1990). Bad storage and disposal
practices associated with reserves pits have lead to their being a source
of benzene, lead, arsenic, and fluoride, even when these components
were not detected in the active mud system (Wojtanowicz, 1991).
The heavy metals and other dissolved solids contents in both the
water and mud (sludge) phases of 125 reserves pits scattered around
he United States were measured in one study, and the total and water
soluble (leachable) concentrations were determined (Leuterman et ah,
1988), The mean metals concentrations of all of the pits varied
significantly with species, with mean concentrations on the order of
a few tens of mg/L. These data are summarized in Table 23. It was
ound that the metals concentrations in the mud phase were generally
higher than in the water phase, indicating that most of the metals were
probably bound to the organic and clay particles and were not readily
available for leaching.
In separate studies, the heavy metals contents of reserves pits in
he U.S. Gulf Coast were also analyzed and found to vary significantly
Wojtanowicz et ah, 1989 and Deuel and Holliday, 1990). In the latter
study, the pit contents were analyzed by the U.S. Environmental
Protection Agency, the American Petroleum Institute, and in a private
study under Louisiana State guidelines. The analysis protocols and
procedures differed in the three studies and yielded somewhat different
esults. The results are summarized in Tables 24 and 25.
3i
Environmental Control in Petroleum Engineering
Table 2-3
Average Elemental Composition of Reserves Pits
Metal
Phase
Concentration (mg/L)
Calcium
Mud
Water
Mud
Water
Mud
Water
Mud
Water
Mud
Water
Mud
Water
Mud
Water
Mud
Water
Mud
Water
Mud
Water
Mud
Water
Mud
Water
Mud
Water
Mud
Water
Mud
Water
Mud
Water
Mud
Water
Mud
Water
207
156
3.97
2.09
56.05
14.47
6.51
0.08
24.46
3.36
17.21
65.47
0.29
0.19
77.67
4.74
313
750
1,819
2,125
0.21
0.07
52.54
5.07
8.79
8.10
135
56
2,204
3,639
582
447
45
0.47
929
551
Chromium (soluble)
Chromium (total)
Lead (soluble)
Lead (total)
Magnesium (total)
Manganese (soluble)
Manganese (total)
Potassium
Sodium
Zinc (soluble)
Zinc (total)
pH
Carbonate
Chloride
Bicarbonate
Hydroxyl
Sulfate
Source: from Leuterman et al., 1988.
Copyright SPE, with permission.
Drilling and Production Operations
37
Table 2-4
Average Elemental Composition of Reserves Pits
Metal
Barium
Chromium
Lead
Zinc
Pit 1 (mg/g)
Pit 2 (mg/g)
Pit 3 (mg/g)
Pit 4 (mg/g)
10.119
0.071
0.044
0.170
8.906
0.024
0.354
0.256
11.088
0.179
0.057
0.148
7.085
0.056
0.037
0.162
Source: from Wojtanowicz et at., 1989.
Copyright SPE, with permission
Table 2-5
Average Elemental Composition of Reserves Pits
Metal
Arsenic
Calcium
Chromium
Barium (total)
Iron
Lead
Magnesium
Manganese
Potassium
Sodium
Zinc
Private Study (mg/g)
API (mg/g)
EPA (mg/g)
0.003
31.0
0.016
29.2
15.1
0.064
3.72
0.273
2.61
2.36
0.120
0.008
47.2
0.017
0.029
71.7
0.081
N/A
N/A
21.2
0.059
4.72
0.393
1.85
3.78
0.189
56,8
0.446
8.10
0.940
N/A
5.62
0.683
Source: from Deuel and Holliday, 1990.
Copyright SPE, with permission.
The heavy metals found in pits are not uniformly distributed in the
pits. Heavy metals are often bound to coarse particulates and tend to
accumulate near the point of discharge. The nonuniform distribution
of metals in a pit needs to be considered when sampling the pit for
metals concentration (Deuel and Holliday, 1990). Other studies, how
ever, reveal no preferential distribution of metals in reserves pits
(Wojtanowicz et al., 1989). Because the migration rate of chromium
out of unlined pits is only a few feet per decade (Campbell and Akers,
1990), reserves pits are not expected to be a major source of chromium
contamination for the environment.
38
Environmental Control in Petroleum Engineering
Regulations for the design and monitoring of reserves pits during
and after drilling can vary significantly with location. Unlined pits are
most commonly used for freshwater mud systems, while pits lined with
an impermeable barrier are used for salt or oilbased mud systems.
Following the completion of drilling of the well, the pits are eventually
dewatered, covered with a few feet of soil, and abandoned.
For offshore applications, steel tanks are used as reserves pits. The
solids, after being separated from the mud, are typically discharged
into the sea, where they settle to the bottom around the drilling rig.
In some areas, however, regulations require that any waste mud and
cuttings be transported to shore for disposal.
2.1.5
Site Preparation
The preparation of drilling and production sites can cause local
impact on the environment, including erosion, soil compaction, and
sterilization. The development of a drilling site involves the construc
tion of roads to the site and a level surface at the site. This con
struction can cause erosion. Erosion control measures like hay bales,
silt fences, riprap, and mulching can be used. Environmentally sound
construction methods are also required, such as slope controls, terrac
ing, wing ditches, and diversion barriers.
The heavy equipment used to prepare a site can compact the soil,
preventing water and nutrients from flowing through the pore system.
This retards root development in plants and limits site restoration after
abandonment. Depending on the site, it may take decades to recover
(Powter, 1990). The level of compaction and its effects on plant growth
depend on soil type and particle size distribution. To date, no good
correlation has been developed to predict the effect of soil compaction
on plant growth. Freeze/thaw and wetting/drying cycles have shown
to be ineffective in loosening compacted soil and restoring normal
water/air circulation.
Drilling sites are often sterilized with herbicides to prevent plant
growth around the well and along rightsofway. This reduces fire
hazards and improves aesthetic appearance, particularly where weeds are
prevalent. Depending on the herbicide and concentration used, how
ever, treated areas can remain devoid of vegetation for many years. Often
an excessive amount has been used to ensure longterm vegetation
control with one application. When this occurs, the site becomes a
Drilling and Production Operations
3§
potential source of contamination through surface runoff and wind
dispersion to adjoining land. Bromacil and tebuthiuron have commonly
been used as sterilization chemicals. These herbicides can become inactive
by applying charcoal to the site at abandonment (Powter, 1990),
2.2 PRODUCTION
The production of oil and gas generates a variety of wastes. The
largest waste stream is produced water, with its associated constituents.
This section reviews both the production process and the wastes that
are generated during production.
2.2.1 Overview of Production Processes
For the oil (or gas) to be produced, a pressure gradient must be
established in the formation on the pore level. This pressure gradient
then forces oil from one pore to the next, and ultimately to the
production well. There are two basic ways for such a pressure gradient
to be established. First is to have a production well with a lower
pressure than that of the surrounding formation. This will cause oil
to flow to the well, where it can be produced. Second is to increase
the pressure in some parts of the formation by injecting fluids. This
will force oil to flow away from the injection wells to lower pressure
production wells. In many reservoirs, a combination of low pressure
at the production well coupled with a high pressure at an injection
well are used.
During production, both water and formation solids are commonly
produced with oil and gas. The produced materials are passed through
separation equipment, where the density differences between the
produced materials are used to separate them.
The first stage of separation normally occurs in a free water knock–
out. This consists of a large tank that allows time for the bulk oil,
gas, and water phases to separate. These tanks are also called wash
tanks, settling tanks, and gun barrels. The output streams from this
equipment consists primarily of gas, water with some oil, and oil with
some water. Solids either settle to the bottom of the tank or are carried
along with the water stream. The performance of these separators has
been reviewed by Powers (1990 and 1993) and the American Petro
leum Institute (1990a).
40
Environmental Control in Petroleum Engineering
The liquid streams exiting the free water knockout are generally in
the form of an emulsion. These emulsions normally require additional
treatment. Emulsions can be broken by adding demulsifiers (chemicals
that cause the water drops to coalesce), by heating the emulsion, by
passing an electrical current through the emulsion (Fang et al., 1991),
or with combinations of these processes. These processes break the
emulsion, allowing the droplets to grow and settle in the gravitational
field. This settling is driven primarily by buoyancy and impeded by
viscous drag, as described by Stokes law. Chemicals used to break
emulsions include surfactants, alcohols, and fatty acids.
The efficiency of the separations equipment in breaking emulsions
depends on the droplet size and density difference between the oil and
water. Small droplets are much more difficult to separate. The droplet
size depends on the interfacial tension between the oil and water and
the shear history of the fluid. If the fluid flows through many shearing
devices at high velocity, e.g., chokes, valves, or pumps, the oil can
be shorn into smaller and smaller droplets. Emulsions are stabilized
by many of the treatment chemicals added to the production stream,
making separations even more difficult.
The hydrocarbon levels in the produced water after exiting dernulsi
fication equipment may still be too high for unrestricted discharge.
Advanced water treatment methods are available that can further lower
the hydrocarbon levels. These advanced methods are discussed in
Chapter 6.
2.2.2
Produced Water
The largest volume waste stream in the upstream petroleum industry
is produced water. For mature oil fields, the volume of produced water
can be several orders of magnitude greater than the volume of pro
duced oil. The environmental impact of produced waters arise from
its chemical composition. Produced water contains dissolved solids and
hydrocarbons (dissolved and suspended), and is depleted in oxygen.
Dissolved Solids
Most produced water contains a variety of dissolved solids. The
most common dissolved solid is salt (sodium chloride). Salt concentra
tions in produced water range between a few parts per thousand to
Drilling and Production Operations
41
hundreds of parts per thousand (ppt). For comparison, seawater con
tains 35 parts per thousand.
In addition to salt, many produced waters also contain high levels
of calcium, magnesium, and potassium, with lower amounts of alumi
num, antimony, arsenic, barium, boron, chromium, cobalt, copper, gold,
iron, lead, magnesium, manganese, nickel, phosphorus, platinum,
radon, radium, silicon, silver, sodium, strontium, tin, uranium, and
vanadium. The concentrations of seven major heavy metals found in
produced water in the Gulf of Mexico are summarized in Table 26.
Lead, nickel, chromium, zinc, nickel, and copper were found to have
the highest concentrations (Stephenson, 1992). Produced water also
contains low levels of naturally occurring radioactive materials. Radio–
active materials are discussed below.
Hydrocarbons
Produced water normally contains dissolved and suspended droplets
of hydrocarbons and other organic molecules that are not removed by
the separations equipment. Hydrocarbon effluent concentrations vary
widely with equipment used. The majority of the hydrocarbon concen
trations in produced water from the Gulf of Mexico are between 10
and 30 mg/L, with virtually all levels less than about 100 ppm (Burke
et al., 1991; Stephenson, 1992). The current U.S. Environmental
Protection Agency limits for the discharge of hydrocarbons in water
Metal
Table 2-6
Heavy Metals Concentrations in Produced Water
Average Concentration
(micrograms/L)
Standard Deviation
(micrograms/L)
27
186
104
315
192
63
170
12
68
180
670
307
17
253
Cadmium
Chromium
Copper
Lead
Nickel
Silver
Zinc
Source: from Stephenson, 1992.
Copyright SPE, with permission.
42
Environmental Control in Petroleum Engineering
or the best available technology (BAT) are 29 mg/L on a monthly
average and 42 mg/L for a daily maximum. Like all regulatory targets,
hese numbers are subject to change.
The concentrations of dissolved hydrocarbons in produced water
depends on the solubility of the hydrocarbon. For discharges in the
Gulf of Mexico, dissolved hydrocarbon concentrations for phenols,
benzene, and toluene were found to be between 1,000 and 6,000
micrograms/L, while the concentrations of high molecular weight
hydrocarbons was considerably lower (Stephenson, 1992). These data
are summarized in Table 27.
Oxygen Depletion
Produced water is invariably oxygen depleted. If discharged, oxygen
depleted water can impact fauna requiring dissolved oxygen for
respiration. Oxygen depletion can be a problem for discharge in
shallow estuaries and canals, particularly if the produced water forms
a layer along the bottom because of its higher density. This dense layer
would be isolated from the atmosphere, limiting its contact with
Table 2-7
Dissolved Hydrocarbon Concentrations in Produced Water
Hydrocarbon
Average Concentration
(rnicrograms/L)
Standard Deviation
(micrograms/L)
4,743
5,771
5,190
700
5,986
4,694
4,850
1,133
1,049
1,318
1,065
221
132
7
889
1,468
896
754
161
18
Gas Production
Phenols
Benzene
Toluene
C2 Benzene
Oil Production
Phenols
Benzene
Toluene
C'2 Benzene
Naphthalene
Other PAHs
Source: from Stephenson, 1992,
Copyright SPE. with permission.
Drilling and Production Operations
43
oxygen. Oxygen depletion is normally not a problem for discharge in
deep water or in highenergy environments because of rapid dilution
of the produced water in the surrounding environment,
2.2.3
Production Chemicals
Produced water is responsible for a variety of problems in oilfield
operations. The most common problems are emulsions, corrosion,
scale, microbial growth, suspended particles, foams, and dirty equip
ment. A variety of chemicals are often added to the water to avoid
those problems.
Emulsion Breakers
As previously discussed, produced water often consists of an oil
inwater emulsion. Chemicals are commonly used to lower the electro
static forces on the oil droplets to allow them to coalesce into larger
droplets. Common chemicals used for this purpose include surfactants,
alcohols, and fatty acids.
Corrosion Inhibitors
Produced water can be very corrosive to production equipment.
Corrosion is caused primarily by the presence of dissolved oxygen,
carbon dioxide, and/or hydrogen sulfide gases. A detailed discussion
of corrosion is given by Jones (1988).
Although produced water is initially oxygen depleted, oxygen can
enter the produced fluid stream as a result of agitation during pumping
or by atmospheric diffusion in holding tanks and surface impound
ments. The oxygen content of water can be minimized by designing
the system to exclude oxygen contact with the water. Carbon dioxide
and hydrogen sulfide can occur naturally in the formation and be
produced with the water. Carbon dioxide forms carbonic acid, which
lowers the pH and increases the corrosivity of the water. Hydrogen
sulfide corrosion can occur as a result of bacterial action on sulfates
and is more often a surface or near surface phenomenon.
Complex inorganic salts like sodium chromate (Na2CrO4), sodium
phosphate (Na3PO4), and sodium nitrite (NaNO3) are also effective in
slowing oxygen corrosion, particularly in high pH environments.
44
Environmental Control in Petroleum Engineering
Sodium chromate, however, adds chromium to the produced water,
Sodium hexametaphosphate (Na6P6Ol8) is used in cooling and boiling
water treatment. Zinc salts of organic phosphonic acids and sodium
molybdate (Na2MoO4) have also been used for corrosion control. Zinc
based inhibitors are less toxic than chromates and should be used if
possible. Organic anionic inhibitors, such as sodium sulfonates and
sodium phosphonates, are also used in cooling waters and antifreeze.
Current regulations may limit the use of some corrosion inhibitors.
Hydrogen sulfide can be removed from produced fluids with a
zinc scavenger. Zinc carbonate (ZnCO3Zn[OH]2) is widely used.
This chemical reacts with hydrogen sulfide, producing insoluble zinc
sulfide (ZnS).
For water injection systems, oxygen causes the largest problems
with corrosion. Oxygen can be removed from water by stripping it
with an inert gas, such as natural gas, steam, or flue gas, by vacuum
deaeration, or by chemical treatment. Oxygen scavengers include
sodium sulfite (NaSO3), sodium bisulfite (NaHSO3), ammonium bisulf
ite (NH4HSO3), sulfur dioxide (SO2), sodium hydrosulfite (Na2S2O4),
and hydrazine (N2H2).
Cathodic protection can be used for external corrosion of casing and
pipes and for internal corrosion of tanks. Both internal and external
surfaces of surface equipment can sometimes be protected with liners
to prevent corrosion. These liners can be hydrocarbon, plastic, metal,
ceramic, or cement based.
Scale Inhibitors
The dissolved solids in produced water are normally in thermo
dynamic chemical equilibrium with the downhole conditions. As water
is produced, however, its temperature and pressure are lowered,
altering the chemical equilibrium. One common result of this altered
chemical equilibrium is the precipitation of inorganic salts in produc
tion equipment, i.e., scale. Scale can plug production equipment,
rendering it useless. Scale is commonly composed of calcium, stron–
tium, and barium sulfates, as well as calcium carbonate. A more
complete discussion of scaling is given by Jones (1988).
Scale can be inhibited by organic phosphate esters of aminoalcohols,
phosphonates, or acrylic acid type polymers (sodium polyacrylate poly–
mers). These chemicals adsorb onto the crystal nuclei when scale first
Drilling and Production Operations
45
precipitates and prevent further growth. Altering the design of the
production system may also minimize the probability of a solution
reaching a saturated state and forming scale in critical flow paths.
Because some oxygen scavengers can produce sulfates which
can react with calcium, barium, and strontium to produce scale, the
addition of oxygen scavengers where scaling may be a problem should
be minimized.
A problem related to scale formation is the precipitation of hydro
carbon solids (paraffin) in production tubing and equipment. Paraffin
precipitation occurs when the temperature and pressure of the crude
oil no longer allow paraffin to remain dissolved in the oil. Various
organic additives are used to inhibit paraffin deposition.
Biocides
Microbial growth (bacteria) in produced water can produce hydro
gen sulfide gas by the chemical reduction of sulfates. Dissolved
hydrogen sulfide gas makes produced gas highly corrosive. In addition
to causing corrosion, the presence of the bacteria themselves can
impact production operations. Bacterial fouling of equipment and
degradation of hydrocarbons can occur. Pads or mats of bacteria, iron
sulfide, and degraded oil can be formed at the oil/water interface in
tanks and separators, rendering them less effective.
To minimize these problems, biocides are often added to the pro
duced water to inhibit microbial growth. Surfactants can also be added
to mobilize the microorganisims and make them more susceptible to
the biocide. Bacteria are rarely completely killed using biocides, so
longterm treatment is usually required once a system is contaminated.
Biocides used include aldehydes, quaternary ammonium salts, and
amine acetate salts. Chlorine compounds are used as biocides in
municipal drinking water systems.
Coagulants
Produced water often contains various amounts of produced
solids. While most of these solids are separated in surface settling
tanks, very small solids (clay particles) may remain suspended in the
water. Coagulants and flocculants can be added to the produced water
stream to agglomerate these fine particles and allow them to settle.
46
Environmental Control in Petroleum Engineering
Coagulants commonly include polyamines and polyamine quaternary
ammonium salts.
Foam Breakers
Some crude oils generate a foam during production. This foam
inhibits the separation of the oil, water, and solids in the production
equipment. Although not commonly needed, foam breakers are avail–
able. Foam breakers include silicones, polyglycol esters, and alumi–
num stearate.
Surfactants
Surfactants (detergents) are regularly used to wash equipment and
decks on offshore rigs. These surfactants commonly include alkyl aryl
sulfonates and ethoxylated alkylphenols.
2.2.4
Well Stimulation
The oil and gas production rate of many wells is restricted by a
low permeability around the wellbore. To increase the production rate,
the permeability is often increased by stimulation. The two most
common forms of stimulation are acidizing and hydraulic fracturing.
Acidizing
Acids are used to dissolve acidsoluble materials around the well
bore to increase the formation's permeability. These acidsoluble
materials can include formation rocks and clays, as well as any
materials added during drilling. A variety of inorganic and organic
acids can be used, depending on the formation. These acids include
hydrochloric, formic, acetic, and hydrofluoric. Additives are also
required to optimize the process.
The most widely used acid is hydrochloric acid. Its main application
is in low permeability carbonate reservoirs. The major reaction prod
ucts produced during acidizing are carbon dioxide, calcium chloride,
and water. Spent acid returned from a well has a high chloride content.
The principal disadvantage of hydrochloric acid is its corrosivity on
tubulars, particularly at temperatures above about 250°F.
Drilling and Production Operations
47
Hydrofluoric acid is used to stimulate wells in sandstone forma
tions. It is normally used in a mixture of hydrochloric or formic acids,
and is used primarily to dissolve clays and muds. The reaction prod
ucts are various forms of fluorosilicates. Like hydrochloric acid, it is
highly corrosive.
Formic acid is a weak organic acid that is used in mixtures during
stimulation. Formic acid is commonly used as a preservative. It is rela
tively noncorrosive and can be used at temperatures as high as 400°F.
Acetic acid is used to dissolve carbonate materials, either separately
or in combination with hydrochloric or formic acid. It is a slowly
reacting acid that can penetrate deep into the formation and is useful
for hightemperature applications. Reaction products are calcium,
sodium, or aluminum acetates. Acetate salts have minimal environ
mental impact. Like other organic acids, acetic acid has a relatively
low corrosivity.
To prevent acids from damaging or destroying tubulars from corro
sion, corrosion inhibitors are normally used. Many commercially
available inhibitors are complex mixtures of organic compounds,
including thiophenols, nitrogen heterocyclics, substituted thioureas,
rosin amine derivatives, acetylenic alcohols, and arsenic compounds,
Most corrosion inhibitors are retained in the reservoir, so very little
is returned with the spent acid.
Highly reactive acids can react immediately with the formation.
Because the benefits of an acid are maximized if the acid is allowed
to penetrate deep into the formation before being spent, additives to
reduce the reaction rate are used. A common way to retard the reaction
rate is to emulsify the acid before injection, with the continuous phase
being the additive. Emulsions retard the reaction rate by physically
limiting the access of the acid to the formation. Commonly used
additives include salts, alcohols, aromatic hydrocarbons, and other
surfactants. Gelling agents, like xanthan gum and hydroxyethyl cellu
lose, alcohols, acrylic polymers, aliphatic hydrocarbons, and amines,
are also used. Retarders such as alkyl sulfonates, alkyl amines, or alkyl
phosphonates are also used to reduce the reaction rate by forming
hydrophobic films on carbonate surfaces.
During production, the spent acid returning to the surface may
become emulsified with crude oil. These emulsions can be stabilized
by the fines released during acidizing. To prevent such emulsions from
forming, demulsifiers (surfactants) can be used. Common demulsifiers
48
Environmental Control in Petroleum Engineering
include organic amines, salts of quaternary amines, and polyoxy
ethylated alkylphenols. Glycol ether can be used as a mutual solvent
for both spent acid and oil.
Wettability agents are used to alter the relative permeability of
emulsions during acidizing and to change the wettability back when
acidizing is complete. The objective of such wettability changes
is to lower the injection pressure by maximizing the relative perme
ability of the emulsion during injection and to maximize the subse
quent production rate by maximizing the relative permeability of
oil after acidizing. Wettability is changed by the use of surfactants
such as ethylene glycol monobutyl ether, methanol, 2butoxy ethanol,
or fluorocarbons.
To lower the pumping pressure during acidizing, friction reducers
are used with acid to reduce its viscosity. Friction reducers allow a higher
injection rate for a given pump size or allow a smaller pump for a given
injection rate. Friction reducers are normally organic polymers that convert
Newtonian acid to shearthinning, nonNewtonian fluid.
Solvents can be used as a preflush with acid to clean oil sludges
and paraffin off of formation particles so they can be better contacted
by the acid. These solvents normally have a high alcohol content, e.g.,
methanol or isopropanol.
Because the local permeability in a formation can vary significantly,
the acid injection profile may not be uniform. To modify the injection
profile and provide a more uniform acidization, fluid loss and diverting
additives like benzoic acid flakes, naphthalene flakes (mothballs), rock
salt, silica flour, or polymers can be used.
Even when corrosion inhibitors are used, some iron compounds
will be dissolved into the acid and carried into the formation. In
some cases, this iron can precipitate in the formation, reducing its
permeability. Complexing agents, like citric, lactic, acetic, and glu
conic acids, or derivatives like ethylene diamine tetracetic acid (EDTA)
and nitrilo triacetic acid (NTA) can be used to inhibit the precipita–
tion of iron.
Hydraulic Fracturing
Hydraulic fracturing increases the permeability around a wellbore
by creating a high permeability channel from the wellbore into the
formation. During hydraulic fracturing, fluids are injected at a rate high
Drilling and Production Operations
49
enough so that the fluid pressure in the wellbore exceeds the tensile
strength of the formation, rupturing the rock.
The most commonly used base fluid for hydraulic fracturing
is water. Water is inexpensive and inflammable. Various hydro
carbons can also be used as a base fluid, particularly where surface
freezing may occur. Acid is also occasionally used when a com
bination of acidizing and hydraulic fracturing is desired. Liquefied
gases, such as carbon dioxide or liquefied petroleum gases, can also
be used, particularly to fracture gas wells. The use of a liquid base
fluid in gas wells can reduce the gas production rate by lowering the
gas relative permeability.
After fracturing, the fluid pressure in the fracture drops when the
well is placed back on production. This allows the fracture to close.
To keep the fracture open during production, solids are injected with
the base fluid to fill the fracture and prop it open. Materials used for
proppants include sand, aluminum pellets, glass beads, walnut shells,
and plastic beads.
To lower the pump size required to fracture the rock, additives are
used to increase the viscosity of the fracturing fluid to enhance its
proppantcarrying capability. To viscosify the waterbased fracture
fluids, polymers such as guar or xanthan gum, cellulose, or acrylics
can be used. These polymers are frequently crosslinked with metal
ions like boron, aluminum, titanium, antimony, or zirconium to further
enhance their viscosity. To viscosify the oilbased fracture fluids,
aluminum phosphate esters are commonly used. Surfactants are also
occasionally used to create a liquidair foam or oilwater emulsion to
be used as the fracture fluid. To prevent degradation of many gels at
high temperatures, stabilizers like methanol and sodium thiosulfate can
be added.
Most polymers and crosslinkers operate in a solution having an
optimum pH. For fluids needing a low pH, buffers of acetic, adipic,
formic, or fumeric acids can be used. For fluids needing a high pH,
sodium bicarbonate or sodium carbonate can be used.
Many formations have sensitive clays that swell during water
injection from the exchange of small cations inside the clays with
larger water molecules. Swelling clays plug the pores, limiting fluid
flow. Clay minerals can also break loose and migrate through the
pore network to lodge in pore throats and limit fluid flow. Clay stabil
izers are often used to prevent such damage. Temporary stabilization
50
Environmental Control in Petroleum Engineering
methods include adding salts to the fluids to minimize exchange of
water molecules with the cations in the clays. These salts are then
returned when the well is placed on production. Salts used as tempo
rary stabilizers include sodium chloride, potassium chloride, calcium
chloride, and ammonium chloride. Permanent stabilizers, such as
quaternary amines and inorganic polynuclear cations like zirconium
oxychloride or hydroxyaluminum, bond to the clay surfaces to stabilize
them. Permanent stabilizers remain in the formation and are not
removed with produced fluids.
When the viscosity of the fracture fluid is increased, the pressure
drop in the pipe is also increased from friction. This results in a higher
pressure at the pump, but a lesser increase in pressure at the formation
face where it is needed. To suppress the pressure drop in the pipe,
high molecular weight polymers can be added to the fracture fluid.
These polymers suppress turbulence, keeping the flow in the pipe
laminar and lowering the friction losses.
A related method for reducing the pressure drop in the pipe is to use
a crosslinking polymer that has a slow gelling time. The crosslinkers
are added to the polymer at the wellhead just prior to injection. The
mixing is timed so that the gel reaches its maximum strength when it
reaches the formation face. This causes the maximum fluid pressure
at the formation face and minimizes the pressure drop down the pipe.
The polymers used to alter the viscosity of fracturing fluids are
subject to bacterial degradation. Bactericides, such as glutaraldehyde,
chlorophenates, quaternary amines, and isothiazoline, are often added
to control the level of bacteria.
To control fluid loss into high permeability zones, fluid loss addi
tives can be added to fracture fluids. These solids include silica flower,
granular salt, carbohydrates, and proteins for waterbased fluids and
organic particulates such as wax, pellets, or naphthalene granules for
oilbased fluids. Another popular fluid loss method is to use an oil
inwater emulsion. This causes twophase flow through the filter cake
along the fracture wall, lowering the relative permeability of the water
through the filter cake.
After a fracture has been created, breakers are used to lower the gel
viscosity so the fracture fluids can be easily removed from the fracture
and not inhibit subsequent production. A common breaker for water
based fracture fluids are peroxydisulfates. Altering the pH by adding
acids or bases is a common way to break oilbased fracture fluids.
Drilling and Production Operations
51
Following hydraulic fracturing, sand is often produced from the
wells. To minimize sand production, chemicals that physically stabilize
the sand around the wellbore can be injected. These chemicals include
plastics like phenol formaldehyde and epoxy resins, together with
alcohol solvents and special refined oils.
2.2.5
Natural Gas Production
As natural gas flows from the ground, it contains a variety
of impurities that must be removed before it can be sold. These
impurities are primarily water vapor, carbon dioxide, and hydrogen
sulfide. The process of removing hydrogen sulfide and carbon dioxide
is called sweetening.
Natural gas also contains fluids like propane, butane, and ethane,
which can be separated from the gas by liquefaction. These natural
gas liquids are more valuable and can be sold at higher prices. Other
materials contained in the gas stream include produced water, pigging
materials for the pipelines, filter media, fluids from corrosion treat
ment, and solids like rust, pipe scale, and produced sand. Cooling
water and used lube oils and filters from compressors are also gener
ated during gas treatment (American Petroleum Institute, 1989).
Natural gas is separated from produced solids and liquids by gravita
tional forces in separators. Natural gas liquids are separated from
the lower molecular weight components by compression, absorption,
and refrigeration.
Water vapor is removed from natural gas by contact with liquid or
solid desiccants. Liquid desiccants include triethylene glycol, ethylene,
and diethylene. Solid desiccants include towers filled with alumina,
silica gel, silicaalumina beads, or molecular sieves. The water is
subsequently removed from the desiccant by heat regeneration, and
the desiccant is reused. The desiccation processes can generate wastes
of glycolbased fluids, glycol filters, condensed water, and solid
dessicants. These materials may contain low levels of hydrocarbons
and treating chemicals. Benzene and other volatile aromatics can
dissolve in glycols and be subsequently emitted when the glycol is
being regenerated for reuse.
Carbon dioxide and hydrogen sulfide are removed from natural gas
by contact with amines. The most common amines are diethanoiamine
(DBA) and monoethanolamine (MEA). Hydrogen sulfide can also be
52
Environmental Control in Petroleum Engineering
removed by contact with sulfinol, iron sponges (finely divided iron
oxide in wood shaving carriers), and caustic solutions. Amines and
sulfinol can be restored for reuse by heat regeneration, but iron
sponges and caustic solutions are spent as the iron is converted to iron
sulfide and other sulfur compounds. Other wastes generated when
removing sweetening natural gas include spent amine, used filter
media, and flared acid gas wastes. Sodium hydroxide is often added
o the amine to prevent corrosion of equipment.
During sweetening, amine compounds are attacked by carbon
dioxide and can break down. The solutions are filtered to remove
he degradation products from the usable amine. The degradation
products form toxic amine sludges that require treatment and disposal
(Boyle, 1990).
During the production of natural gas, hydrates can form from
the gas and water vapor. Hydrates are a slushy, icelike substance
hat can plug the production tubing and equipment. Various chemi–
cals, primarily methanol and ethylene glycol, are sometimes added to
gasproducing wells to lower the freeze point of hydrates to inhibit
heir formation.
2.2.6
Other Operations
A variety of other operations associated with the production of oil
and gas generate wastes that have the potential to impact the environ
ment. These wastes include wastewater from cooling towers, water
softening wastes, contaminated sediments, scrubber wastes, used filter
media, various lubrication oils, and site construction wastes.
Cooling towers are used for a variety of processes during oil and
gas production. The cooling water used in these towers often contains
chromebased corrosion inhibitors and pentachlorophenol biocides.
In many areas, produced water is reinjected into the reservoir to
assist hydrocarbon recovery. Unfortunately, the level of dissolved
solids, particularly hardness ions (calcium and magnesium), is often
oo high to be used because they readily precipitate and can plug the
ormation. Thus, before produced water can be reinjected, it must be
softened to exchange the hardness ions with softer ions, e.g., sodium.
The most common way to soften produced water is through ion
exchange. There are two major ion exchange resins (substrates) that
are commonly used: strong acid resins, using sulfonic acid, and weak
Drilling and Production Operations
83
acid resins, using carboxylic acid. Strong acid resins can be regener
ated simply by flushing with a concentrated solution of sodium chlor
ide. Weak acid resins, however, must be regenerated by flushing with
a strong acidlike hydrochloric or sulfuric and then neutralizing it with
sodium hydroxide.
During oil production, sand and shale sediments are often produced
with the oil. These sediments are separated out in the surface equip
ment. They normally collect in tank bottoms and must be periodically
removed. These solids are normally mixed with oil, forming a sludge.
Sediments can also be contaminated with oil and other materials from
spills and leaks from equipment.
The hydrocarbon content of oilcontaminated sediments can exceed
4% by weight (Deuel, 1990). These sediments may also contain heavy
metals or hydrogen sulfide (Brommelsiek and Wiggin, 1990). Total
heavy metal concentrations in produced solids are generally low, as
indicated in Table 28 (Cornwell, 1993). It is not known whether the
differences in heavy metal concentrations for native soils in Alaska,
shown in Table 22, and for produced solids, shown in Table 28, are
from production activities or just natural variations in geology.
To remove the suspended solids that are not removed by settling,
produced fluids are often passed through filters. The filter media must
be frequently replaced or backwashed. The filled filters or filter
backwash must be disposed.
The operations of much of the oilfield equipment, including stuffing
boxes, compressors, and pumps, requires lubrication oil. As this oil
is used, it changes its composition, making it potentially unsuitable
for future use. The used lube oil must be replaced with fresh oil, and
the used oil must be disposed of.
In areas where lease crude is burned, e.g., where steam is injected
to recover oil, the combustion gases may need to be scrubbed to
remove pollutants like sulfur dioxide. One way to remove sulfur
dioxide from combustion gases is to bubble it through aqueous solu
tions containing caustic chemicals like sodium hydroxide or sodium
carbonate. Sulfur dioxide dissolves into water, forming sulfuric acid,
which is neutralized by the caustic. Another form of scrubber uses
various amines. Typical wastewaters can have very high levels of
dissolved solids, as indicated in Table 29 (Sarathi, 1991).
In cold climates, like Alaska's North Slope, methanol is used for
freeze protection of equipment. It is used to protect pipelines, shutin
54
Environmental Control in Petroleum Engineering
Table 2-8
Heavy Metal Concentrations
of Produced Solids
Metal
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium
Cobalt
Copper
Lead
Mercury
Molybdenum
Nickel
Selenium
Silver
Thallium
Vanadium
Zinc
Fluoride
Total (ppm, wt)
11
105
326
<1
<1
93
10
64
22
5
16
176
<1
1
17
27
214
76
Source: from Cornwell, 1993.
Copyright SPE, with permission.
water injection wells, and as a component of waterbased hydraulic
fracturing fluids.
2.2.7
Radioactive Materials
Many drilling sites and production facilities have radioactive mate
rials associated with them. Some of these radioactive materials,
primarily radioactive tracers or logging tools, are deliberately brought
to the site for use, while other materials are naturally occurring and
are called naturally occurring radioactive materials (NORM).
Radioactive Sources and Tracers
Radioactive sources are used primarily during logging with wire
line tools. Both gamma ray and neutron sources are available. These
Drilling and Production Operations
55
Table 2-9
Composition of Scrubber Wastewater
Constituent
Aluminum
Bicarbonate
Boron
Calcium
Carbonate
Chloride
Copper
Fluoride
Iron
Magnesium
Manganese
Nitrate
Phosphate
Potassium
Sodium
Sulfate
Sulfur Dioxide
Zinc
Total Dissolved Solids
Concentration (ppm)
0,4
31,183
20.8
11.2
0
2,237
0.5
5.2
32
0.43
0.63
0.5
0.6
101
53,000
79,013
420
5.3
148,438
Source: from Sarathi, 1991.
Copyright SPE, with permission.
sources are sealed within the logging tools and are normally not
a problem.
Radioactive tracers are commonly used in injection wells to deter
mine points of fluid entry into the formation (injection profile),
hydraulic fracture height, and/or fluid leaks in the cement behind
casing. The tracer is injected into the wellbore and a gamma ray detector
is then logged through the well to determine depths at which the radio
activity is high. Commonly used radioactive tracers for liquid phase
measurements include antimony124 (as antimony oxide), iridiurn192 (as
potassium hexachloroiridate), scandium46 (as scandium chloride), and
iodine131 (as sodium iodide). Krypton85 has been used as a vapor
phase tracer. Radioactive proppant is also used during hydraulic
fracturing to monitor the location of the fracture behind casing.
Radioactive proppants typically use the same isotopes that are used
for liquid phase tracers.
5§
Environmental Control in Petroleum Engineering
Naturally Occurring Radioactive Materials
Naturally occurring radioactive materials (NORM) are found virtu
ally everywhere on the earth, including ground and surface waters
(Judson and Osmond, 1955). During the production of oil and gas,
radioactive materials that naturally occur within the earth can be
coproduced. Although the concentrations of NORM are usually very
low, these materials can be concentrated during production; the con
centrated levels can become high enough to cause a health hazard if
improperly managed.
There are four radionuclides most commonly found in NORM in
the upstream petroleum industry: radium226, radium228, radon222,
and lead210. Radium226 is probably the nuclide with the greatest
potential for environmental impact for the petroleum industry. Other
radioactive materials are also found, but in significantly lower amounts.
Radium (both 226 and 228) is highly soluble and is produced as a
dissolved solid with the produced water. The levels of radium in
produced water vary significantly. Although most wells do not produce
significant amounts of NORM, typical concentrations in wells having
NORM have been reported to vary between 12,800 picocuries per
liter (pCi/1). Much higher concentrations, however, have also been
reported (St. Pe et al., 1990; Miller et al., 1990; Snavely, 1989;
Stephenson, 1992). In comparison, the natural radium levels in surface
waters are typically less than 1 pCi/1. Drinking water standards for
radioactive materials are typically 5 pCi/1, and discharge standards for
open water are 30 pCi/1, although these regulatory limits can vary.
Radium is coprecipitated with barium, calcium, and strontium
sulfate as scale in tubulars and surface equipment during production.
This concentrates the radium and makes the scale radioactive. Radium
can also be concentrated in various production sludges through its
association with solids in the sludge. NORM concentrations of several
hundred thousand pCi/gm have been found in scale in piping and
surface equipment. Concentrations in excess of 8,000 pCi/gm have
been measured in the soil at pipe cleaning yards (Carroll et al., 1990).
The presence of NORM, however, can be easily identified with gamma
ray detectors.
Radon222 is a naturally occurring gas that is found in some
produced water and natural gas liquids. This gas comes out of solution
as the pressure is reduced during production. Because it is a gas, it
Drilling and Production Operations
5?
normally is not concentrated in sufficient quantities to cause environ
mental impact, although it can be temporarily concentrated in low
lying areas.
Lead210 is of particular concern to the natural gas liquids industry
(Gray, 1993). When lead210 is formed, it precipitates on equipment
surfaces, forming an extremely thin layer of radioactive film.
Although significant levels of NORM have been seen at some
production operations, it is not normally encountered at drill sites. The
drilling process does not provide a way for significant concentrations
of NORM to accumulate.
2.3 AIR EMISSIONS
A wide variety of air pollutants are generated and emitted during
the processes of finding and producing petroleum. These air pollutants
include primarily oxides of nitrogen (NOx), volatile organic compounds
(VOCs), oxides of sulfur (SOx), and partially burned hydrocarbons
(like carbon monoxide and particulates). Dust from construction and
unpaved access roads can also be generated.
Volatile hydrocarbons, including aromatics, are emitted during the
regeneration of glycol from natural gas dehydration (Grizzle, 1993;
Thompson et al., 1993). Halon gases are used at many drilling and
production sites for fire suppression. These gases have been identified
as an ozonedepleting chlorofluorocarbon (CFC), and their use releases
them to the atmosphere.
2.3.1 Combustion
The largest source of air pollution in the petroleum industry is the
operation of the internal combustion engines used to power drilling
and production activities, such as drilling rigs, compressors, and
pumps. These engines can be powered by either natural gas or diesel
fuel. The two primary pollutants emitted from these engines are oxides
of nitrogen, primarily NO and NO2, and partially burned hydrocarbons.
The nitrogen oxides are commonly referred to as NOx. During combustion,
about 3.5 pounds of NOx can be generated for each barrel of fuel burned.
Emissions of NOx from petroleum industry operations in 1975
totaled 1.3 million U.S. tons. This level was about 11% of the total
NO emissions from all stationary sources in the United States and
58
Environmental Control in Petroleum Engineering
6% of the total emissions from all sources. About 46% of the NOx
emitted by the petroleum industry was from gas processing activities,
21% from production activities, and 22% from refineries. Crude oil
transport emitted 5.2% of the petroleum industry NOx, onshore drilling
emitted 4.2%, and product transport emitted 0.9% (American Petrol
eum Institute, 1979).
NOx is formed at high combustion temperatures when molecular
oxygen dissociates into individual oxygen atoms. Atomic oxygen
readily reacts with atmospheric nitrogen to form NOx. Methods to limit
the formation of NO include combustion modifications to lower the
flame temperature during combustion and flue gas treatment to remove
any NOx that has formed. However, little can be done during drilling
and production operations to lower NOx emission, other than to
purchase low NOx generating equipment and operate it as recom
mended by the manufacturer.
Partially burned hydrocarbons are emitted during combustion when
the fuel/air mixture is incorrect. The most common partiallyburned
hydrocarbons from internal combustion engines powered by natural gas
are formaldehyde and benzene (Meeks, 1992). About 25 pounds of
formaldehyde and 1.5 pounds of benzene can be generated per million
cubic feet (MMcf) of fuel burned. For fuels containing benzene,
ethylbenzene, toluene, or xylene (BETX), about 3% of those com
pounds will pass through the engine and be emitted.
Another major source of air pollutants is the operation of heater
treaters, boilers, and steam generators. These types of equipment also
emit NOx and partially burned hydrocarbons like carbon monoxide. If
a sulfurbearing fuel is used, sulfur oxides, primarily SO2 and SO3
(referred to as SOx), can also be emitted. For a crude oil having a
sulfur content of 1.1%, about 7.5 pounds of sulfur will be released
for every barrel of fuel burned. Table 210 shows the typical emission
levels of an oilfired steam generator operating at different levels
(Sarathi, 1991). For reference, a steam generator operating at 50 mil
lion Btu/hr can inject steam into three to five wells. The data in this
table were adjusted for 365 days of continuous operation.
2.3.2
X
Emissions from Operations
A number of operations at production facilities emit volatile mate
rials into the air. Operations that can cause emissions include the use
Drilling and Production Operations
Table 2-10
Typical Steam Generator Emission Levels
Operating Level
(Million Btu/hr)
5
10
20
50
59
S02
(tons/year)
N02
(tons/year)
Particulates
(tons/year)
Hydrocarbons
(tons/year)
21
66
151
275
10.3
23
53
96
2,9
6.4
15
27
0.43
0.91
2.0
3.8
Source: adapted from Sarathi, 1991.
Copyright SPE, with permission.
of fixed roof tanks, wastewater tanks, loading racks, and casing gas
from thermal recovery operations. A more detailed discussion of the
emissions from a typical onshore oil and gas production facility is
provided by Sheehan (1991) and Smith (1987).
During the operation of fixed roof tanks, volatile hydrocarbons can
be emitted into the atmosphere. There are three major sources of
emissions from these tanks: breathing losses, working losses, and
flashing losses. Breathing losses arise from a change in vapor volume
from changes in temperature and barometric pressure. Working losses
are caused by changes in the tank's fluid level. Flashing losses occur
when dissolved gas flashes to vapor from pressure drop changes
between the tank and the production line. A detailed description on
calculating emissions from fixed roof tanks has been prepared by the
American Petroleum Institute (1991).
Open tanks, sumps, and pits can be sources of emissions for volatile
hydrocarbons. The emission rates depend on the ambient temperature,
surface area of the fluid exposed to the atmosphere, and composition
of the hydrocarbon.
Another operational source of air emissions is the transfer of oil
rom tanks to trucks. These emissions occur when the vapors in the
rack are displaced by the entering fluid.
During production from thermal recovery projects, hot fluids are
produced at the production well. Hydrocarbon vapors, carbon dioxide,
and various sulphur compounds can be produced with the oil or from
he casing annulus. To prevent these gases from escaping into the
atmosphere, they can be collected and processed in a casing vapor
recovery system (Peavy and Braun, 1991). Such systems can remove
60
Environmental Control in Petroleum Engineering
99% of the hydrocarbon vapors and 95% of the sulfur in the casing
gas. Because of the sales value of the condensed hydrocarbon vapors,
these systems can pay out within a few years,
2.3.3
Fugitive Emissions
Another source of air pollutants are the fugitive emissions of
volatile hydrocarbons. These are hydrocarbons that escape from pro
duction systems through leaking components like valves, flanges,
pumps, compressors, connections, hatches, sight glasses, dump level
arms, packing seals, fittings, and instrumentation. Valves are usually
the most common components that leak. These emissions generally
result from the improper fit, wear and tear, and corrosion of equipment.
Although the leak rate from individual components is normally small,
the cumulative emissions from an oil field containing a large number
of components can be significant.
A comprehensive study of fugitive hydrocarbon emissions from
petroleum production operations revealed that an average of about
5% of all components in field locations leak (American Petroleum
Institute, 1980). A breakdown of how often each type of component
leaked is given in Table 211. Components in gas service have a leak
rate that is about an order of magnitude higher than components in
liquid service. The leak rate at offshore production facilities is signifi–
cantly lower than at onshore facilities,
Table 2-11
Fugitive Emissions from Petroleum Operations Equipment
Component
Valve
Connection
Sightglass
Hatch
Seal packing
Diaphragm
Meter
Sealing mechanism
Total/Average
Total Number Tested
% Leaking
25,089
138,510
676
358
1,246
1,643
92
5,591
173,205
8.4
3.4
1.3
6,1
25.9
19.4
5,4
10.9
4.7
Source: American Petroleum Institute, 1980.
Reprinted by permission of the American Petroleum Institute,
Drilling and Production Operations
81
Because of the cost of obtaining fugitive emission data, emission
rates are typically measured carefully at only a few facilities. The data
obtained are then normalized to the number and type of fittings to be
used at other facilities. One such set of generic fugitive emission
factors for a production facility that is based on the number of produc
tion wells and the gas/oil ratio is given in Table 212.
More accurate sets of fugitive emission factors can be based on the
number of valves, connections, fittings, flanges, and similar equipment
at a facility. The estimate for the total fugitive emissions would then
be the sum of the average emissions from each piece of equipment
(Schaich, 1991). Table 213 provides a list of average emission factors
for various types of equipment.
Past studies indicate that emission factors such as those given in
Table 213 can overestimate emissions by several orders of magnitude.
A more accurate method of estimating fugitive emissions is to measure
how many pieces of equipment are leaking and apply one set of fugitive
emission factors to the components that are leaking and a second set to
the components that are not leaking. A set of these generic fugitive
emission factors is given in Table 214. In this table, a fitting is
assumed to leak if the concentration measured by a handheld analyzer
is greater than 10,000 ppmv (parts per million by volume).
If a more refined measurement of emission concentration at a piece
of equipment is made, an even more accurate set of fugitive emission
factors can be generated. One such set of factors for three emission
ranges is given in Table 215. An even more refined approach would
(text continued on page 64)
Table 2-12
Generic Fugitive Emission Rates for Production Facilities
Number of Wells
<!0
10-50
>50
<10
10-50
>50
Source: from Sheehan, 1991.
Copyright SPE, with permission.
Gas/Oil Ratio
Emission rate
(Ibm/well/day)
<500
<500
<500
=>500
=>500
=>500
2.56
1.44
0.09
6.85
2.89
4.34
62
Environmental Control in Petroleum Engineering
Table 2-13
Generic Fugitive Emission Factors for Production Equipment
Fluid
Emission
Factor
(kg/hr/source)
Gas
Light liquid
Heavy liquid
Light liquid
Heavy liquid
Gas/vapor
Gas/vapor
All
All
All
0.0056
0.0071
0.00023
0.0494
0.0214
0.228
0.104
0.00083
0.0017
0.0150
Equipment
Valves
Pump seals
Compressor seals
Pressure relief devices
Flanges
Openended lines
Sampling connections
Source: from Schaich, 1991.
Reproduced with permission of the American Institute of Chemical Engineers.
Copyright © 1991 AIChE. All rights reserved.
Table 2-14
Fugitive Emission Factors Based on Leak Determination
Equipment
Valves
Pump seals
Compressor seals
Pressure relief
devices
Flanges
Openended lines
Service
Emission
Factor:
Leaking
(kg/hr/source)
Emission
Factor;
Nonleaking
(kg/hr/source)
Gas
Light liquid
Heavy liquid
Light liquid
Heavy liquid
Gas/vapor
0.0451
0.0852
0.00023
0.437
0.3885
1.608
0.00048
0.00171
0.00023
0.012
0.0135
0.0894
Gas/vapor
All
All
1.691
0.0375
0.01195
0.0447
0.00006
0.00150
Source: from Schaich, 1991.
Reproduced with permission of the American Institute of Chemical Engineers.
Copyright © 1991 AIChE. All rights reserved.
Table 2-15
Fugitive Emission Factors for Three Leakage Rates
Equipment
Valves
Pump seals
Emission Factor:
1,00110,000
(kg/hr/source)
Emission Factor:
> 10,000
(kg/hr/source)
Gas
Light liquid
Heavy liquid
Light liquid
Heavy liquid
Gas/vapor
Gas/vapor
All
All
0.00014
0.00028
0.00023
0.00198
0.0038
0.01132
0.0114
0.00002
0.00013
0.00165
0.00963
0.00023
0.0335
0.0926
0.264
0.279
0.00875
0.00876
0.0451
0.0852
0.00023
0.437
0.3885
1.608
1.691
0.0375
0.01195
Source: from Schaich, 1991.
Reproduced with permission of the American Institute of Chemical Engineers.
Copyright © 1991 AlChE. All rights reserved.
b
3
Oq
3
Product
Compressor seals
Pressure relief devices
Flanges
Openended lines
Service
Emission Factor:
01,000 ppm
(kg/hr/source)
o
3
64
Environmental Control in Petroleum Engineering
(text continued from page 61)
be to develop correlations between the emission rates and the concen
trations measured by a handheld detector. One set of such correlations
is given in Table 216.
The biggest problem with using emission factors with measurements
made with handheld detectors is that the local concentration of
emitted hydrocarbons varies considerably with local conditions. Condi
tions that can affect these measurements are wind speed, pressure in
fitting, composition of hydrocarbon in fitting, and location of detector
when taking the measurement.
2.3.4
Emissions from Site Remediation
Another source of air pollution is from the cleanup of petroleum
contaminated sites. Many cleanup practices for hydrocarbons spilled
on soil result in volatile hydrocarbons being emitted into the air and
transported from the spill site. The most common hydrocarbon spilled
that causes air pollution is gasoline. Models have been developed to
estimate the pollutant levels associated with three types of soil cleanup
technologies: soil extraction, vacuum extraction, and air stripping (U.S.
Environmental Protection Agency, 1989).
Soil extraction is commonly used when contaminated soil is dumped
in a pile to be treated and/or disposed of at a later date. When liquid
gasoline and air are present in the soil, the concentration of volatile
organic carbons (VOCs) will build until it reaches local equilibrium.
Source
Valves
Valves
Pump Seals
Flanges
Table 2-16
Fugitive Emission Rates Based on Correlation
Service
Gas/vapor
Light liquid
All
All
Equation
Q
Q
Q
Q
=
=
=
=
3.766 x 10~535 C0693
8.218 x lO^ 4342 C 047
2.932 x 1Q534 C0898
2.10 x 10 4733 C0.818
Q is the emission rate in Ibm/hr.
C is the measured maximum concentration at the fitting in ppm-v,
Source: from Schaich, 1991.
Reproduced with permission of the American Institute of Chemical Engineers.
Copyright © 1991 AlChE. All rights reserved.
Drilling and Production Operations
§5
The VOC and benzene levels are typically higher for this remediation
method than for other methods, but have shorter durations of emission.
Typical VOC emissions for a soil pile having an area of 2,000 ft2 are
between 50 and 200 Ibm/hr, depending on the temperature. Benzene
emissions for the pile typically range from 0.5 to 2 lbm/hr.
One way to extract the volatile hydrocarbon components in soil is
by vacuum extraction. Vacuum extraction consists of drilling a well
through the contaminated soil and pulling a vacuum in the well. The
lower pressure forces air into the pile, and volatilized compounds
are vacuumed with the air into the well and removed from the
pile. Because soil is treated in place, vacuum extraction can be less
expensive and less disruptive than other methods. Maximum emission
rates tend to be under 50 lbm/hr for VOCs and under 2 lbm/hr for
benzene, The duration of emissions tends to be on the order of weeks
to months.
Volatile hydrocarbons can also be removed from contaminated water
that has been pumped from the ground by air stripping. In this process,
the contaminated water is allowed to trickle over packing material in
an air stripping tower. Clean air is simultaneously circulated through
the packing material. The volatile hydrocarbons vaporize into the air
and are released to the atmosphere. The removal efficiency depends
on the contaminant, but is typically 99% to 99.5%. Emissions of
volatile hydrocarbons tend to be between 0.5 to 4 lbm/hr, with benzene
releases between 0.1 and 0.5 lbm/hr. Although air stripping has the
lowest emission levels of the three methods discussed here, it typically
has the longest duration,
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CHAPTER 3
The Impact of Drilling
and Production
Operations
Many of the materials and wastes associated with drilling and
production activities have the potential to impact the environment. The
potential impact depends primarily on the material, its concentration
after release, and the biotic community that is exposed. Some environ
mental risks may be significant, while others are very low.
The most common measure of the potential environmental impact
of a material is its toxicity. Toxicity occurs when a material causes a
deleterious effect on an organism, population, or community. These
effects can range from temporary disorientation to lethality. This
chapter reviews how toxicity is measured and then summarizes many
of the toxicities measured for materials associated with drilling and
production activities.
3.1 MEASURING TOXICITY
The toxicity of a substance is a measure of how it impairs the life
and health of living organisms following exposure to the substance.
In most cases, the effects of the substance on human life and health
is of primary importance. Toxicity is determined through bioassays by
exposing laboratory animals to different amounts of the substance
in question. The resulting effects on the health of the animals are
observed. For petroleum industry wastes, common test species used
for marine waters are the mysid shrimp (Mysidopsis bahia) and
sheepshead minnow (Cyrinidon variegatus}, while fathead minnow
71
72
Environmental Control in Petroleum Engineering
Pimephales promelas) and daphnid shrimp (Ceriodaphnia dubia) are
used for fresh waters.
Two types of toxicity measurements are commonly used: dose and
concentration. The dose is the concentration of a substance that has
been absorbed into the tissue of the test species, while the concentration
s a measure of the concentration of a substance in the environment
hat the species lives in. Toxicity measurements using concentration
also include a time interval of exposure.
The dose is the mass fraction of the substance in the animal tissue
(milligram of substance per gram of tissue, mg/g) when a particular
effect has been observed. A dose that is lethal to 50% of the animals
s called LD50, while the lowest dose that is lethal, i.e., the dose
esulting in the first death, is called LDLO. The dose levels required
or any particular effect also depend on how the animal is exposed—
by injection, ingestion, or inhalation.
The concentration is the fraction of the substance in air or water
hat causes a particular effect when the target animal is placed in that
environment. It is normally given either as a mass fraction in parts
per million (ppm) or as mass per unit volume in milligrams per liter
(mg/1). A lethal concentration that kills 50% of the animals within a
given period of time is called LC5(). Similarly, the lowest lethal
concentration for the same period of time is called LCLO. Concen–
ration is the toxicity measure most commonly used for materials
associated with the petroleum industry.
If a material is highly toxic, then only a small concentration will
be lethal and the numerical values of the lethal doses and concentrations—
LD50, LDLO, LC50, and LCLO—would be low. Conversely, a high
value of these parameters indicates low toxicity. LC50 values on the
order of 10 are normally considered highly toxic, while values on the
order of 100,000 are considered nontoxic. The length of exposure to
a substance can be divided into descriptive types, as indicated in
Table 3 1. Exposure that causes an immediate effect is called acute,
while repeated, longterm exposure is called chronic.
There are a number of significant limitations to bioassays for
oxicity testing. These limitations must be considered when
new regulations are being considered or laboratory test protocols are
being developed.
One limitation to most bioassay testing for toxicity is that the tests
yield only acute lethal concentrations. They provide no data on the
The Impact of Drilling and Production Operations
73
Table 3-1
Exposure Types
Exposure Type
Duration of Exposure
Acute
Subacute
Subchronic
Chronic
Less than 24 hours
Less than 1 month
13 months
More than 3 months
sublethal or longterm effects of the tested substances. For sublethal
effects, a related toxicity parameter, EC50 can also be used. This
parameter is the concentration that would result in adverse effects in
test species after an exposure of a specified duration. Few data are
available on EC values, however, because they are difficult and
expensive to quantify. A related sublethal toxicity parameter is the
NOEC (no observable effect concentration), the concentration at or
below which no effects are observed.
Another limitation to bioassays is that they are conducted in a
laboratory and do not necessarily represent the field conditions that
would actually be encountered if exposure occurred. Field conditions
normally involve different concentrations and different mixtures of
potentially toxic materials. Because regulations are normally based on
laboratory data, these differences can lead to regulations not reflecting
the actual risks in the field.
A third difficulty with laboratory bioassays is that they do not
provide adequate information about chronic effects, including the
mutagenic or carcinogenic activity of a substance. Bioassays normally
consist of exposing the test animal to a single, highlevel dose of the
substance in question. Such acute exposure may not induce tumors in
the test animal, even if a chronic exposure of the same substance and
same total dose could. Such timedependent responses have been
observed with poly aromatic hydrocarbons.
The problem with measuring mutagenic or carcinogenic activity
with bioassays is that such activity takes time to appear and be
identified. Many substances, called mutagens, can alter the structure
of DNA molecules in individual cells. Most mutations result in the
death of the individual cells affected, with no reproduction of the
mutation. If a mutated cell survives and results in future birth defects,
74
Environmental Control in Petroleum Engineering
he substance is called teratogenic. If the mutation results in cancer,
he substance is called carcinogenic. As a rule, nearly all carcinogens
are also mutagens, but not all mutagens are carcinogens.
For nonmutagenic or noncarcinogenic substances, a threshold dose
s assumed to exist, below which there is no toxic effect. The threshold
dose depends on the ability of the organism to detoxify and excrete
he substance and repair any damage through normal biological pro
cesses. If an organism is exposed to a dose higher than one that can
be repaired by normal biological processes, then toxic impact will
occur. The magnitude of this impact will increase as the dose increases
over the threshold dose. Although some substances are toxic in high
concentrations, they may be essential in low concentrations for normal
biological processes. These required substances include trace minerals
and heavy metals commonly found in petroleum operations. Bioassays
are generally not able to determine this information. For carcinogenic
or mutagenic substances, however, it is assumed that there is no
hreshold dose. The impact is assumed to increase with the dose over
all exposure levels.
Another significant limitation to bioassays is the time it takes for
results to be obtained. Bioassays typically take two to three weeks to
be completed. A related difficulty is that these tests are normally
conducted offsite, which requires shipping of the fluid samples and
delays in starting the tests. These delays can affect test results because
he fluid chemistry can change over time. All of these difficulties
prevent onsite decisions from being made about the fluid system,
particularly drilling muds. They can result in a drilling mud from an
offshore platform being shipped to shore for more expensive disposal,
when it could legally be discharged overboard. A considerable effort
s underway to develop more rapid bioassays for drilling fluids,
particularly those that can be performed onsite.
One potentially valuable method for rapid toxicity characterization
s the Microtox method (Hoskin and Strohl, 1993). In this method, a
marine luminescent bacterium, Photobacterium phosphoreum, is used.
These bacteria emit light as part of their metabolic processes. Exposure
o a toxic substance interferes with these processes and results in a
reduction in their light output. An advantage of the Microtox method
s that the test is conducted in 15 minutes. A related process for
measuring the toxicity of materials is the cumulative bioluminescence
of Pyrocystis lunula (Wojtanowicz et al., 1992). The correlation
The Impact of Drilling and Production Operations
75
between these two bioluminescence methods with each other and with
mandated mysid shrimp toxicity assays, however, has not been good,
Part of this poor correlation is from the poor reproducibility of the
mysid shrimp toxicity tests between different laboratories. Mysid
shrimp assays are discussed below in the section on drilling fluids,
Another rapid toxicity assay that has been studied is the fertiliza
tion rate of sea urchins. In this test, sea urchin sperm and eggs are
collected, exposed to the substance being tested, and then combined.
The fraction of eggs fertilized is then measured. Like the biolumi–
nescence tests, the fertilization assays correlate poorly with the mysid
shrimp toxicity tests (American Petroleum Institute, 1989f).
Another approach to toxicity testing is to develop correlations
between chemical characteristics of the substance and the bioassays.
One such correlation was attempted for a highweight lignosulfonate
drilling fluid (American Petroleum Institute, 1985c). The chemical
characteristics studied include pH, redox potential, sulfide concen
tration, dissolved chromium, saturated aliphatic hydrocarbons, non
volatile aromatic hydrocarbons, .straightchain alkanes, volatile aro
matic hydrocarbons, unidentified volatile hydrocarbons, and bacterial
activity. Dissolved chromium was found to correlate the best with the
mysid shrimp toxicity for the mud liquids. Unidentified volatile
hydrocarbons correlated the best for the toxicity of the solids. These
correlations, however, were poor, accounting for only about 20% of
the toxic effects.
Although bioassays are conducted on animals, the results are often
used to determine acceptable levels for human exposure. Animal
toxicity data are extrapolated to humans, using factors like body weight
and a variety of safety factors. Based on these extrapolations, a variety
of human health and safety guidelines have been developed.
Human safety guidelines include threshold limit values—time
weighted average (TLVTWA), threshold limit values—short-term
exposure (TLVSTEL), threshold limit value—ceilings (TLVC), and
reference dose (RfD). The TLVTWA is the timeweighted average
concentration for a normal 8hour workday and 40hour workweek to
which nearly all workers can be chronically exposed without adverse
effects. The TLVSTEL is the highest shortterm exposure to which a
worker can be exposed without the worker experiencing irrita
tion, chronic or irreversible tissue change, or narcosis at a level that
impairs judgment or work efficiency. The TLVC is the concentration
76
Environmental Control in Petroleum Engineering
hat should not be exceeded during the work day. TLV values are
developed by the American Conference of Governmental Industrial
Hygienists (ACGIH). Reference doses (concentration per mass of
issue) are an estimate of a daily exposure level to humans that is
likely to occur without an appreciable risk of deleterious effects during
a lifetime. Table 32 provides an example of a reference dose for
several hydrocarbons.
These guidelines have been promulgated into rules and regulations
by the Occupational Safety and Health Administration (OSHA). These
rules are referred to as permissible exposure levels (PEL). TLV values
are guidelines based on scientific evidence. PEL values are legal rales
based on health, economic, and safety considerations. The National
Institute of Occupational Safety and Health (NIOSH) also develops
recommended exposure limits (RELs). Like TLV values, RELs are
guidelines, not rales.
One source of toxicity data in the United States are Material Safety
Data Sheets (MSDSs). For any substance sold in the United States,
he manufacturer must provide an MSDS that summarizes all known
health and physical hazard information about the substance. The
oxicity information provided on MSDSs is most commonly LD50 data.
Although the format of MSDSs can vary, they must provide the
ollowing information:
1. Manufacturer's name, address, phone number, and date of MSDS
preparation.
2. Identity of material (chemical and common names).
Table 3-2
Calculated Reference Dose
for Petroleum Hydrocarbons
Hydrocarbon
Mineral spirits
Diesel fuel no. 2
Lubricating oil
Crude oil
Source: Ryer-Power et al., 1993.
Copyright SPE, with permission.
Reference Dose
(mg/kgday)
0.015
0.04
0.11
0.04
The Impact of Drilling and Production Operations
77
3. List of hazardous ingredients, with exposure limits.
4. Physical and chemical characteristics, including boiling point,
melting point, density, solubility in water, appearance, odor,
vapor density, and vapor pressure,
5. Fire and explosion hazard data, including flash point, flam
mability limits, extinguishing media, special firefighting pro
cedures, and unusual fire and explosion hazards.
6. Reactivity data, including chemical stability, incompatibility with
other chemicals and materials, hazards of decomposition or
byproducts, and whether the material polymerizes.
7. Health hazard data, including exposure routes (inhalation, skin,
or ingestion), acute and chronic health hazards, toxicity data,
carcinogenicity, signs and symptoms of exposure, medical condi
tions aggravated by exposure, and emergency procedures (includ
ing first aid).
8. Precautions for safe handling and use, including steps to be taken
if the material is spilled or released, firstaid procedures for
exposure, method for disposal, and precautions for handling
and storage.
One limitation to MSDS data is that it is often incomplete; normally,
it only summarizes existing information from the literature. The
manufacturer, in many cases, is not required to conduct additional
research on the material. Such research is generally very costly and
timeconsuming. Because of this, the quality of MSDS data can vary
considerably from chemical to chemical and from vendor to vendor.
Even though manufacturers may not be required to conduct bioassays
on the materials they offer for sale, bioassays are often required before
a permit to discharge a material to the environment can be obtained,
3.2 HYDROCARBONS
Crude oil contains thousands of different types of hydrocar
bon molecules. The toxicities and potential environmental impacts
of the different molecules vary considerably. Numerous studies
have been conducted on the environmental impact of hydrocarbon
exposure. In this section, the major types (families) of hydrocarbons
and their toxicities are discussed, and related environmental impact
studies are reviewed.
78
Environmental Control in Petroleum Engineering
3.2.1
Hydrocarbon Families
Crude oil contains thousands of different kinds of hydrocarbon
molecules, making it very difficult to characterize. Crude oil can also
contain significant quantities of other elements, like sulfur, nitrogen,
oxygen, and heavy metals, further complicating its characterization.
Crude oil is typically composed of between 50% and 98% hydro
carbons. Other important components can be sulfur (010%), nitrogen
(01%) and oxygen (05%). Heavy metals can be found in the parts
permillion level (National Research Council, 1985).
The molecules in crude oil, however, can be grouped into a few
families having similar properties. These families are distinguished
primarily by how the carbon atoms bond to each other and by the
presence of elements other than carbon and hydrogen. Table 33
summarizes most of the families of hydrocarbons found in crude oil.
These families are discussed below.
Table 3-3
Families of Hydrocarbons
Family Name
Alkanes
Alkenes (olefins)
Alkynes (acetylenes)
Cyclic Alkanes (naphthenes,
cycloparaffins)
Aromatics
Polyaromatics
Alcohols
Acids
Amines
Examples
Methane
Ethane
Propane
Methene
Propene
Ethyne
Propyne
Cyclopropane
Cyclobutane
Benzene
Toluene
Naphthelene
Tetralin
Methanol
Ethanol
Acetic acid
Methyoamine
Formula
CH4
C2H6
C3H8
C2H4
C2H2
C3H4
C3H6
C4H8
C6H6
C6ft H5r> CH
C10H8
C!0H12
CH3OH
C2H5OH
C2H4OH
CH3NH2
The Impact of Drilling and Production Operations
7§
The simplest family consists of the alkanes. These molecules contain
only carbon and hydrogen and are distinguished by the single bond
between each carbon atom. All other bond sites are occupied by
hydrogen. The chemical formula has the general form CnH2n+r This
family is also called paraffins or saturated hydrocarbons, because it
contains the maximum possible amount of hydrogen. The chemical
structure of some common alkanes is shown in Figure 31. Although
H
i
H-C —H
Methane
H
H
i
P.
I
H
H
i
C
I
H
H
H
C-H
I
H
LJ
I
H
H
H
Ethane
H
i
H
H
i
H
H
1
1
H - c --c -- C -C-H
1
1
1
1
H
H
H
H
n-Butane
Propane
H
H-C -H
H
H
I
I
H-C - C — C — H
I
!
i
H
H
H
Isobutane
Figure 3-1. Structure of some common alkanes.
80
Environmental Control in Petroleum Engineering
he carbon chain can branch, as seen by the two isomers of butane,
he carbon chain does not form continuous loops.
The next family of hydrocarbons is the alkenes or olefins. These
molecules are like the alkanes, except that one of the carbontocarbon
bonds is a double bond instead of a single bond. For each double bond
between the carbon atoms, there are two fewer bond sites available
or hydrogen (one from each carbon associated with the double bond.
Because of this, the chemical formula has the general form CnH,n.
The chemical structure of some common alkenes is shown in Fig
ure 32. Alkenes are unsaturated, because not all possible bond sites
contain hydrogen.
The third family of hydrocarbons is the alkynes or acetylenes. These
molecules are characterized by a triple bond between two of the carbon
atoms. The resulting chemical formula has the general form CnH2n2.
The chemical structure of some common alkenes is shown in Fig
ure 33. Alkynes are also unsaturated.
H
1
H
1
H
1
C= C
1
1
H
H
H
1
H
1
H-C —C = C
1
1
H
H
Ethene
(Ethylene)
Propene
(Propylene)
Figure 3-2. Structure of some common alkenes.
H
__
H
C= C
Ethyne
(Acetylene)
!
H
H
C
1
H
_
C == C
n
Propyne
Figure 3-3. Structure of some common alkynes.
H
The Impact of Drilling and Production Operations
81
The fourth family of hydrocarbons is the cyclic alkanes, also called
naphthenes or cycloparaffins. These hydrocarbons have the carbon
chain loop back upon itself, forming a ring or cyclic structure. All
carbontocarbon bonds are single bonds. The chemical formula for
these compounds has the general form CnH2n. The chemical structure
of some common naphthenes is shown in Figure 34. In accordance
Cyclopropane
Cyclopentane
Cyclobutane
Cyclohexane
Decalin
(bicyclodecane)
Figure 3-4. Structure of some common cyclic alkanes.
82
Environmental Control in Petroleum Engineering
with common organic chemistry symbolism used for more complex
molecules, only the carbontocarbon bonds are shown in this figure.
The carbon atoms are found at the intersections of the bonds, and the
hydrogen atoms are inferred around the carbon atoms such that the
four carbon bond sites are all occupied. For naphthenes, two hydrogen
atoms are found with each carbon atom. Some hydrocarbons can have
multiple rings, with shared carbon atoms. An example of one of these
condensed rings is decaline.
The fifth family of hydrocarbons is the aromatics. These compounds
are also ring structures, but each carbon has only one hydrogen atom
and the remaining bond sites are shared among the adjacent carbon
atoms. This results in very stable carbontocarbon bonds. These bonds
are conveniently written as an alternating doublesingle bond, as shown
in Figure 35, although each carbontocarbon bond is identical. Ben
zene is the simplest of the aromatic hydrocarbons. Other aromatics can
be created by replacing one of the hydrogen atoms with a carbon
chain, as shown in Figure 35. Three isomers of xylene are also
possible, with only one isomer shown in the figure.
A sixth family of hydrocarbons is the polyaromatic hydrocarbons.
Condensed aromatics are also known as polycyclic aromatics, poly
aromatic hydrocarbons (PAH), or polynuclear aromatics (PNA). These
condensed ring structures have aromatic rings sharing carbon atoms
with other rings. Two examples are shown in Figure 36. The poly
aromatic fraction of crude oil ranges between about 0.2% and 7,4%.
Other families of hydrocarbons contain atoms other than carbon and
hydrogen. Alcohols are formed by replacing a hydrogen atom with an
oxygenhydrogen atom pair. Organic acids are formed by replacing the
three hydrogen atoms at the end of a hydrocarbon chain with a double
bonded oxygen atom and an oxygenhydrogen atom pair. Amines are
formed by replacing a hydrogen atom with a nitrogen atom having two
hydrogen atoms bonded to it. The chemical structures of several such
compounds are shown in Figure 37.
Other families of hydrocarbons can be created if a carbon atom in
the carbon chain or ring is replaced by other elements. Sulfur and
nitrogen are commonly found as a carbon substitute. Heavy metals are
found in complex compounds called porphyrins.
A final family of hydrocarbons is the asphaltenes. These are large
polyaromatic hydrocarbons that contain sulfur, oxygen, or nitrogen.
They contain typically three to ten ring structures. Pure asphaltenes
The Impact of Drilling and Production Operations
83
H
I
H —C—H
Toluene
Benzene
H
H
I
H-C-H
H-C-H
H
H
H
Xylene
Ethylbenzene
Figure 3-5. Structure of some common aromatics.
are solids and are insoluble in crude oil, although they can be dispersed
in oil as a colloidal suspension.
3.2.2
Hydrocarbon Toxicity
A number of bioassay tests have been conducted to determine the
toxicity of various hydrocarbons on marine animals. The toxicity of
84
Environmental Control in Petroleum Engineering
Naphthalene
Tetralin
(Tetrahydronaphthalene)
Figure 3-6. Structure of some common polyaromatic hydrocarbons.
H
1
H~C — OH
ii
H
H
H
1
1
H - C — C " OH
1
1
i
1
H
Methanol
H
Ethanol
H
H
C — OH
H
II
O
Acetic Acid
H
N
H
Methylamine
Figure 3-7. Structure of mixed hydrocarbon compounds.
The Impact of Drilling and Production Operations
85
hydrocarbons has been found to vary considerably and generalizations
cannot be easily made. Factors that affect toxicity include molecular
weight, hydrocarbon family, the organism exposed to the hydrocarbon,
and lifecycle stage of the organism exposed (egg, larva, juvenile, or
adult). For mixtures of hydrocarbons, such as crude oil, the toxicity
also depends on the history of the exposure.
For hydrocarbons of a similar type (the same family), the toxicity
ends to increase with decreasing molecular weight. Smaller molecules
end to be more toxic than large molecules. Light crude oils and
refined products tend to be more toxic than those of heavy crude
oils, because heavy crude oils have a higher average molecular weight.
For similar molecular weight hydrocarbons, the toxicity varies with
family. The toxicity of hydrocarbon families generally increases in the
following order: alkanes, alkenes, cycloparaffins, aromatics, and poly
aromatic hydrocarbons.
Some of the least toxic hydrocarbons include dodecane and higher
paraffins. In fact, these high molecular weight paraffins are used in
cooking, food preparation, and candles. The most toxic hydrocarbons
are the lowboilingpoint aromatics, particularly benzene, toluene,
ethylbenzene, and xylene. Because of their similar properties, these
four aromatic molecules are commonly referred to as BTEX. The most
oxic hydrocarbons also tend to have a high solubility in water. A high
solubility makes a molecule more accessible for uptake by plants
and animals.
The toxicity of a given hydrocarbon varies considerably with the
organism exposed. Factors that also affect the toxicity to a particular
organism include the general health of the organism and whether the
organism is already stressed. Stress factors include water salinity,
emperature, and food abundance. The toxicity of crude oil to some
fish can be twice as high in seawater as in fresh water. The toxicity
of a particular hydrocarbon also appears to increase with decreasing
emperature. Synergistic effects from the presence of other toxins can
also significantly alter the toxicity of specific hydrocarbons.
The toxicities (LC50) for a variety of aromatic and polyaro
matic hydrocarbons are shown in Tables 34a and 34b (National
Research Council, 1985). The LC50 values for many aromatic hydro
carbons are less than about 5 ppm, although some have values as high
as 28 ppm. From these tables, it can also be seen that the toxicity
s higher (lower LC50) for higher molecular weight polyaromatic
86
Environmental Control in Petroleum Engineering
Table 3-4a
Summary of Bioassay Tests on Marine Organisms
Hydrocarbon
Benzene
Toluene
mXylene
oXylene
pXylene
Ethylbenzene
Trimethylbenzene
Naphthalene
Methylnaphthalene
Test Species
Test
Duration
(hr)
Grass Shrimp
Crago
Striped Bass
Grass Shrimp
Crago
Striped Bass
Cancer
Salmon Fry
Palaemonetes
Striped Bass
Cancer
Crago
Striped Bass
Cancer
Crago
Striped Bass
Palaemonetes
Striped Bass
Cancer
Copepod
Cancer
Palaemonetes
Salmon Fry
Amphipod
Neanthes
Paneaus aztecus
Cyprinodon
Palaemonetes
Cancer
Copepod
Penaeus aztecus
Cyprinodon
Copepod
96
96
96
96
96
96
96
24
96
96
96
96
96
96
96
96
96
96
96
24
96
96
24
96
96
24
24
96
96
96
24
24
24
Source: after National Research Council, 1985.
Copyright © 1985, National Academy of Sciences.
Courtesy of National Academy Press, Washington, D.C.
LC50
(ppm)
27
20
6
9,5
4
7,5
28
5.5
3.5
9
12
1
1!
6
2
2
0.5
5
13
3.5
2
2.5
I
2.5
3,5
2.5
2.5
1
•>
1.5
0.5
3.5
2
The Impact of Drilling and Production Operations
8?
Table 3-4b
Summary of Bioassay Tests on Marine Organisms
Hydrocarbon
Dimethylnaaphthalene
Trimethylnaphthalene
Fluorene
Dibenzothiophene
Phenanthrene
Methylphenanthrene
Fluoranthene
Test Species
Test
Duration
(hr)
Palaemonetes
Cancer
Neanthes
Penaus aztecus
Copepod
Cyprinodon
Neanthes
Cancer
Palaemonetes
Neanthes
Cyprinodon
Palaemonetes
Cyprinodon
Palaemonetes
Neanthes
Neanthes
Neanthes
96
96
96
24
24
24
96
24
96
96
96
96
96
24
96
96
96
LC50
(ppm)
0,5
0,5
2
0.5
0,5
5
2
0.25
0.25
1
1.5
0,25
3
0.25
0.5
0.25
0.5
Source: after National Research Council, J985.
Copyright © 1985, National Academy of Sciences.
Courtesy of National Academy Press, Washington, D.C
hydrocarbons than the single ring aromatics of benzene, toluene,
ethylbenzene, and xylene (BTEX).
The high toxicity of aromatic hydrocarbons relative to other hydro
carbons can be seen by comparing the 96hour mysid shrimp toxicity
for drilling muds using diesel oil to that using mineral oils. Diesel oil
contains as much as 60% aromatic components, while some mineral
oils contain less than 1%. LC50 values for diesel are around 2,000 pprn,
while those for some mineral oils are greater than 1,000,000 ppm, in
which case less than 50% of the test species died during the test period
(Derkics and Souders, 1993). As discussed below in the section on
drilling fluids, the mysid shrimp test protocol dilutes the oil with sea
water by a factor of nine before the test is conducted. Thus, these
88
Environmental Control in Petroleum Engineering
mysid shrimp data cannot be directly compared to data that were
obtained using a protocol that does not require the same dilution.
The presence of mineral oilbased mud and synthetic oilbased mud
(polyalphaolefin) on cuttings at concentrations up to 8.4% had no
significant effect on the growth of mud minnows (Fundulus grandis),
The uptake of mineral oils, however, was higher than that of synthetic
oils, suggesting that synthetic, highmolecular weight liquids may have
a lower toxicity (Rushing et al., 1991; Jones et al., 1991).
For a particular organism, the lifecycle stage at which exposure
occurs can impact how toxic a material is. Table 35 shows the results
of bioassays on four organisms as a function of lifecycle stage for
exposure to No. 2 fuel oil. From this table, it can be seen that some
species have a higher tolerance at younger stages, while other species
have a higher tolerance at older stages (National Research Council,
1985), In most species, however, the adults are more tolerant of
Table 3-5
Effect of Life-Cycle Stage on Fuel Oil Toxicity
Species
Brown Shrimp:
Postlarvae
Small juveniles
Large juveniles
White Shrimp:
Postlarvae
Juveniles
Grass Shrimp:
Larvae
Postlarvae
Adults
Polychaeta:
4 segments
18 segments
32 segments
Adults (40 segments)
96hour LC50
(ppm)
6.6
3.8
2.9
1.3
1.0
1.2
2.3
3.6
8.3
5.8
5.5
4.0
Source: after National Research Council, 1985.
Copyright © 1985, National Academy of Sciences.
Courtesy of National Academy Press, Washington, D.C.
The Impact of Drilling and Production Operations
81
exposure to hydrocarbons than the young. For all of the species
ncluded in this table, however, the LC50 values are below 10 ppm.
ndicating a high toxicity at all lifecycle stages.
An important factor affecting the toxicity of crude oils is their
history before any organisms are exposed. Because the most toxic
hydrocarbons are also the most volatile, they rapidly evaporate from
a release site. Within a few days after a crude oil release, only higher
molecular weight hydrocarbons remain, so the toxicity of the remain
ng crude oil is lower. Hydrocarbons in water also tend to adsorb onto
suspended sediments, making them much less bioavailable to marine
organisms than hydrocarbons in solution or dispersion in water. This
urther lowers the toxicity of released crude oil. If the sediments
accumulate on the bottom of the sea, they can accumulate in estuarine
organisms. The accumulation and metabolism of these compounds,
however, vary with species (American Petroleum Institute, 1989e).
Impact of Crude Oil on Marine Animals
The actual impact of hydrocarbon exposure on marine animals is
more complex than simple bioassay tests reveal. Oil at sublethal
concentrations can significantly alter the behavior and development of
marine organisms. These effects, however, are difficult to quantify. The
problem of determining sublethal toxicity is further compounded
because different species have different reactions and there is mixed
effect when multiple toxins are present. Although there is a tremendous
amount of scatter in the data, most threshold concentrations of crude
oil in water for effects to be observed for eggs, embryos, and larvae
of marine fish are between 0.01 and 5 mg/1 (National Research
Council, 1985).
Behavioral changes from exposure to hydrocarbons are primarily
hose involving motility, while in higher organisms, changes affect
avoidance, burrowing, feeding, and reproductive activities. Behavioral
changes in feeding have been observed at hydrocarbon concentrations
as low as a few microgm/1. Other measures of sublethal effects include
changes in respiration, the ratio of oxygen consumed to nitrogen
excreted, biochemical enzyme assays, and cellular activity. The respira
ory rate following exposure is usually reduced, although in some
cases, it is increased. The level of exposure for respiratory impact for
ish and planktonic crustaceans in the laboratory is less than 1 mg/1.
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Environmental Control in Petroleum Engineering
Continued hydrocarbon exposure also lowers the growth rate of animals
(National Research Council, 1985).
Exposure to hydrocarbons can adversely affect the development of
organisms in some species at concentrations below 1 mg/1. Some
species (annelids, gastropods, and copepods) show no longlasting
damage, while other species (corals, bivalves, and some crustaceans)
can suffer longterm damage at an oiled site (National Research
Council, 1985).
The impact of hydrocarbon exposure also depends on whether the
hydrocarbon is dissolved or dispersed as suspended droplets. For
shrimp, the toxicity of dispersed crude oil was found to decrease with
decreasing amounts of total aromatic hydrocarbons (benzene, alkyl
benzenes, and naphthalenes). For sand lance fish, however, the impact
could not be tied directly to the concentration of aromatics in the
water. Instead, it was postulated that the oil droplets attached to
their eggs and cut off their oxygen supply (American Petroleum
Institute, 1985a).
One concern with crude oil spills is their potential impact on the
behavior of migratory salmon. Because salmon identify their home
water by smell, there was concern over whether their sense of smell
would be affected by passing beneath a spill so that they could not
recognize their home water. Studies have shown that as long as the
fish pass back into uncontaminated water, their homing ability is not
affected (American Petroleum Institute, 1985b; American Petroleum
Institute, 1986a; American Petroleum Institute, 1987a).
The effects of spilled crude oil on the reproductive success of
Pacific herring (Culpea harengus pallasi) have also been studied
(American Petroleum Institute, 1985a). No effect in fertilization rates
or total percentage of eggs successfully hatched were observed. How
ever, exposure to oil significantly increased the frequency of abnormal
larvae. These abnormalities included spinal deformities, swollen peri
cardial regions, and yolk sac compartmentalization. The amount of oil
droplets adhering to the eggs apparently controlled the frequency of
abnormal larvae rather than the total oil concentration in the water. It
was not certain whether this increase of abnormal larvae resulted from
the toxic compounds of the oil passing to the eggs or from oxygen
deprivation from the oil droplets covering the egg.
The most common impact of crude oil on birds is by direct contact,
Oil coats their feathers, causing them to lose their waterrepellance
The Impact of Drilling and Production Operations
SI
and thermal insulation. The birds then sink and drown or die of
hypothermia. Oil can also be ingested by the birds during preening
of oiled plumage. Although this oil becomes distributed throughout the
body, there is no evidence that ingested oil is a primary cause of death
among birds (National Research Council, 1985).
Nonlethal exposures of birds to crude oil significantly reduces
hatchling success and fledgling success in a dosedependent manner
(American Petroleum Institute, 1988). Adult petrels were most sensit
ve to contaminant exposure late in the incubation period and early
n the posthatchling period. Pollutantrelated decreases in reproductive
success were probably associated with temporary abandonment of the
nesting burrow by adults. Treated adults generally returned to normal
behavior in the second season following exposure. The primary con
cern for marine birds appears to be the immediate effects on adult
mortality and the resulting population dynamics. The effects of sublethai
exposures may be significant only in areas where exposure is chronic,
Crude oil also impacts phytoplankton and zooplankton. The effect
of crude oil is to inhibit growth and photosynthesis (for phytoplank–
on) at concentrations in the range of 110 mg/1 (National Research
Council, 1985).
The effect of oil on marine mammals is highly variable. Fur
insulated mammals lose their ability to thermally regulate their tem
perature as their oilcontaminated fur loses its insulating capacity. The
loss of thermal insulation creates a higher metabolic activity to regulate
body temperature, which results in fat and muscular energy reserves
being rapidly exhausted. This can result in the animal's death by
hypothermia or drowning. Many species show no avoidance response
to oiled areas. Chronic contact of marine mammals with oil may also
result in skin and eye lesions (National Research Council, 1985).
Impact of Crude Oil on Ecosystems
Only a few studies have been conducted on the chronic effects of
hydrocarbon releases on ecosystems. No apparent longterm impacts
on the productivity of ecosystems have been observed. In all cases,
he affected areas recovered after the hydrocarbon source had been
removed, although full recovery could take a number of years. One
difficulty with ecosystem studies, however, is that little is known about
ecosystems that have not been exposed to hydrocarbons. This makes
§2
Environmental Control in Petroleum Engineering
it difficult to determine what lasting effects hydrocarbons do have on
ecosystems (National Research Council, 1985).
One ecosystem that is chronically exposed to hydrocarbons from
petroleum production is the Gulf of Mexico. Natural variations in this
ecosystem, however, may completely mask any effects of oil pro
duction (National Research Council, 1985), Natural variations in the
ecosystem cause large changes in the diversity and number of organ
isms present at any particular location. These natural variations include
the effects of the Mississippi River discharging into the Gulf. The
Mississippi River has a low salinity, a low oxygen concentration, a
high concentration of nitrogen fertilizers, and a high concentration of
suspended solids. These conditions vary significantly from those of
the marine environment and can have a significant natural impact on
the ecosystem. Because of the chaotic nature of the turbulent discharge
of the Mississippi River, this impact occurs over a large portion of
the Gulf.
A study of hydrocarbon and heavy metal contamination on the
continental shelf of the Louisiana coast in the Gulf of Mexico revealed
contamination of hydrocarbons and heavy metals near offshore plat
forms (U.S. Bureau of Land Management, 1981). No measurable
impact on the ecosystem could be observed from the presence of the
offshore platforms. In areas having a very low background level of
hydrocarbons in the sediments, elevated hydrocarbon levels were
observed at distances up to 2,000 m from the platform. In areas having
a relatively high background level of hydrocarbons, no concentration
of hydrocarbons in the sediments around the platform was observed.
All levels were, however, below those for public concern. Essentially
no accumulation of hydrocarbons in organisms around platforms was
observed. Some concentration of heavy metals occurred, but insufficient
data were obtained for a reliable statistical analysis. The Mississippi River,
with its fresh water, high sediment load, and low dissolved oxygen
content, had a greater measured impact on the benthic ecosystem than
did the offshore platforms.
Contamination of sediments by polyaromatic hydrocarbons from
routine discharges of produced water into shallow estuaries have been
reported as far away as one kilometer (Rabalais et al., 1990). The
effect of hydrocarbon contamination on the benthic community around
such discharge points was correlated to the hydrocarbon contamination
level. Macrobenthic fauna were missing or greatly affected when the
The Impact of Drilling and Production Operations
93
polyaromatic hydrocarbon concentrations were on the order of 1 ppm.
Reduced fauna concentrations were observed for polyaromatic hydro
carbon concentrations on the order of 0.1 ppm.
A fouryear study was conducted on the ecological effects, chemical
fate, and microbial responses of marsh systems following crude oil
spills (American Petroleum Institute, 198la). The effects of oil spills
on phytoplankton were short lived, with a recovery within seven days
to the levels found in the control area. The effects of oil on standing
marsh plants were severe during the first year following exposure.
Growth during the third year was, on the average, as great as in the
control area, although growth in the high plant concentration areas was
still lower.
The impact of chronic exposure to tar balls on intertidal biota in a
rocky shore community in Bermuda have also been studied (American
Petroleum Institute, 1984a). There was no correlation between the
presence or amount of tar on the shore and the reproductive status of
the six intertidal species studied. Snail size was correlated with the
presence of tar, however. Little accumulation of hydrocarbons in
tissues of intertidal animals was found. Tar balls are believed to come
from discharged tanker ballast tanks, with the level of tar on a beach
being controlled by the amount of direct exposure to constant wave
action, topography, and configuration of the shoreline. Tar balls are
accumulated almost exclusively in the upper intertidal and splash zone.
One important way to gain information about the effects of chronic
exposure of ecosystems to crude oil is to study areas having natural
oil seeps. Studies at natural seeps at Coal Oil Point in the Santa
Barbara Channel, California, have shown that the level of macrofauna
s reduced when the hydrocarbon content in the sediments is high
(National Research Council, 1985; American Petroleum Institute,
1980). The reason for the lower faunal level is the reduced amount
of oxygen, high sulfide content, and high level of dissolved hydro
carbons (mostly aromatics) in the surrounding water. Aromatic concen
rations in water have been measured as high as 1.3 mg/1. Areas with
ower seepage (less than 0.1 mg/1) show little or no impact.
A separate study of a major natural seep area near Santa Barbara,
California, that leaks 5070 barrels of oil per day revealed little
mpact. The growth rate of resident marine organisms near the seeps
was not affected, the total biomass (plant and animal life) and biomass
of individual species groups were not related to the presence of
94
Environmental Control in Petroleum Engineering
hydrocarbons in sediments, and all species expected to be in the area
were indeed present. Fish feeding around the seeps did show high
levels of enzyme activity needed to break down and digest the toxic
oil compounds (American Petroleum Institute, 1984b).
Impact on Human Health
The impact of hydrocarbons on human health depends somewhat
on whether exposure was from ingestion, inhalation, or dermal (skin)
contact and on whether the exposure was acute (shortterm) or chronic
(longterm).
The acute effects of ingestion may include irritation to the mouth,
throat, and stomach, and digestive disorders and/or damage. Small
amounts of hydrocarbons can be drawn into the lungs, either from
swallowing or vomiting, and may cause respiratory impact such as
pulmonary edema or bronchopneumonia.
The chronic effects of ingestion may include kidney, liver, or
gastointestinal tract damage, or abnormal heart rhythms. Prolonged
and/or repeated exposure to aromatics like benzene may cause damage
to the bloodproducing system and serious blood disorders, includ
ing leukemia. The metabolism of aromatic hydrocarbons after
ingestion can result in the creation of mutagenic or carcinogenic
derivatives, even if the original hydrocarbon is relatively nontoxic.
(National Research Council, 1985). A number of PAHs have been
inked to cancer of the skin, lung, and other sites on the body. There
s no epidemiologic evidence for human cancer from intake of PAH
contaminated food, however. Most human exposure to PAHs comes
from nonpetroleum sources, including cigarette smoke, fossil fuel
combustion products, and food.
The acute symptoms of hydrocarbon exposure by inhalation may
nclude irritation of the nose, throat, and lungs, headaches and dizziness,
anesthetic effects, and other central nervous system depression effects.
These symptoms can occur at air concentrations of 0.5 mg/1 for 30
minutes (Hastings et al., 1984). Epileptictype seizures may occur
months after a high acute exposure to gasoline vapors, and permanent
brain damage has been reported. Acute toxic effects are not commonly
observed, however, in gas station attendants and auto mechanics.
Chronic effects of inhalation exposure to hydrocarbons containing
high concentrations of aromatic compounds, including gasoline, can
The Impact of Drilling and Production Operations
95
be weight loss from loss of appetite, muscular weakness and cramps,
sporadic electroencephalography irregularities, and possible liver and
renal damage.
Exposure of eyes and skin to hydrocarbons may result in irritation,
mechanical or chemical damage to eye tissue, or dermatitis. Longterm
exposure to vacuum distillates has caused skin cancer in animals.
Exposure to petrochemicals, particularly polyaromatic hydrocarbons,
increases susceptibility to skin infections, including skin cancer when
there is simultaneous exposure to sunlight (Burnham and Bey, 1991;
Burnham and Rahman, 1992).
One potential source of hydrocarbon exposure to humans is inges
tion of hydrocarboncontaminated food, particularly seafood. Studies
have shown that most organisms cleanse themselves of hydrocarbons
within a matter of weeks after being removed from the source of
contamination. This cleansing time, however, depends upon the con
taminated organism.
The exposure levels of humans to polyaromatic hydrocarbons from
crude oil may be lower than those from other, more common sources
like grilled food and combustion products, or from naturally occurring
sources like coffee, grains, and vegetables (American Petroleum
Institute, 1978).
Suggested standards for human exposure to petroleum hydrocarbons
varies with the specific hydrocarbon, but ranges between 25 and 430
ppm (National Research Council, 1985). Permitted occupational expo
sure levels to benzene are on the order 10 ppm, but vary with the
prevailing regulations.
Impact on Plant Growth
Hydrocarbons also impact plant growth when released on land.
Levels of oil and grease above a few percent in soils (by weight) have
shown degradation of plant growth. Levels below a few percent have
shown an actual enhancement of some crop growth. Recovery of an
exposed site after a onetime hydrocarbon release usually occurs after
a few months (Deuel, 1990). A level of 1% oil and grease is recom
mended as a practical threshold where the hydrocarbons become
detrimental to plant life (American Petroleum Institute, 1989b).
Airborne hydrocarbons emitted during blowouts can also impact
plant growth around the wellhead. Longterm growth rate reductions
96
Environmental Control in Petroleum Engineering
have been observed in coniferous forest growth following blowouts
at distances as great as 2 km from the wellhead (Baker, 1991).
3.3 SALT
Salt (sodium chloride) in low concentrations is essential to the
health of plants and animals. At concentrations different from the
naturally occurring levels found in a given ecosystem, however, salt
can cause an adverse impact.
3.3,1 Impact on Plants
The impact of salt on plants arises primarily from an excess salt
concentration in the cellular fluids of the plants or from an alteration
in the soil structure in which the plants grow. The primary impact of
an abnormal salt concentration in cellular fluids is the disruption of
the fluid chemistry balance within cells. This disruption inhibits
cellular growth, water uptake, and the overall health of the plants.
Growth of nonmarine plants is impaired at total dissolved salt concen
trations between about 1,500 and 2,500 mg/1, although this threshold
level varies significantly with plant type, how the water is applied,
and whether the soil is kept saturated. Salt concentrations below about
1,000 mg/1 seem to improve some plant growth (Vickers, 1990).
When salt was spread over soil in the form of salty drilling muds,
the yield of brome grass was reduced when the concentration of
chloride exceeded about 1,000 kg Cl/hectare for potassium and sodium
chloride, and about 50 kg Cl/hectare for a freshwater gel. The plant
yield for intermediate chloride application levels was higher than that
of control plots (Macyk et al., 1990).
Salt can indirectly impact plant growth by altering the physical
properties of soil. When saline water is discharged on land, it can alter
the pore structure of the soil by causing compaction, limiting the
access of air and water to the plant roots. The impact varies, however,
with salinity level and plant type. If the total dissolved solids content
is above about 2,800 mg/1, salt can build up in the soil (Vickers, 1990).
Excess sodium in soil can also cause clays to disperse, lowering
the permeability of the soil. This can form an impenetrable surface
crust that hinders the emergence of seedlings and limits the availability
of nutrients such as iron, manganese, calcium, and magnesium to the
The Impact of Drilling and Production Operations
i?
plants "(Kaszuba and Buys, 1993). On the other hand, the addition of
clays from drilling muds can increase the water holding capacity of
sandy/coarsetextured soils, improving plant growth.
A number of ways to measure the salinity of soils has been developed,
These measurements include directly measuring the electrical conductivity
of the soil and various measurements of sodium concentration.
The electrical conductivity (EC) of a solution is a measure of the
otal amount of cations and anions dissolved in water. These ions can
nclude sodium (Na), calcium (Ca), magnesium (Mg), potassium (K),
chloride (Cl), sulfate (SO4), bicarbonate (HCO3), carbonate (CO3), and
hydroxide (OH). The electrical conductivity is the reciprocal resistance
of the solution. Table 36 summarizes the effects of different EC values
on crops (U.S. Salinity Staff, 1954). A level of salinity that will not
adversely impact most vegetation, land, or groundwater resources from
he onetime discharge is one at which the electrical conductivity of
he discharged brine is less than 4 mmho/cm. This level will limit the
eduction of crop yields to less than 15% (Deuel, 1990).
The electrical conductivity is related to the total dissolved solids
(TDS) concentration in the water. TheTDS is the weight of residue
after all of the water has been evaporated. The TDS has units of mass/
volume of solution. The relationship between EC and TDS is given
as follows:
TDS = A*EC
(31)
where A is an empirical constant equal to about 640 (Tchobanoglous
and Burton, 1991). The units of the constant are cmmg/mmho/liter.
Table 3-6
Effect of Electrical Conductivity (EC) on Crops
EC Range
(mmhos/cm)
02
24
48
816
>16
Source: U.S. Salinity Staff,
Effect
Negligible
Yield of very sensitive crops impacted
Yield of many crops impacted
Only tolerant crops still produce
Only very few tolerant crops still produce
1954.
98
Environmental Control in Petroleum Engineering
The most common impact of brine on plants is that it increases the
osmotic pressure of the soil solution. Osmosis is a process that controls
the movement of water between solutions, with water flowing from
lower to higher osmotic pressure. Plants have an osmotic pressure in
their cells, which varies from species to species. If the osmotic
pressure in the soil solution outside the plant exceeds that inside the
cell, water cannot flow into the plant. High osmotic pressure produced
by soluble salts also retards water imbibition by seeds, resulting in
decreased germination and slower seedling emergence rates, and
disrupts the uptake of nutrients in plants.
The osmotic pressure (OP) is related to the EC through the follow
ing equation (Deuel, 1990):
OP = 0.36*EC
(32)
In this equation, the osmotic pressure is in atmospheres and the
electrical conductivity is in mmho/cm.
The capacity of a soil to adsorb positively charged ions (cations)
is called the cation exchange capacity (CEC). The exchange
able cations in a soil are those held on surface exchange sites and
are in equilibrium with the soil solution. The measure of the degree
that the exchange sites are saturated with sodium is called the
exchangeable sodium percentage (ESP) and is calculated through
the following equation:
ESP(%) =
CEC
* 100
(33)
where NaX is the amount of exchangeable sodium. Both the CEC and
NaX are expressed in units of meq/100 g. In fertile soils, the most common
exchangeable cations are calcium and magnesium. These ions are less
soluble than sodium and do not affect plant growth to the same degree.
For ESP greater than 15%, some soils can lose their structure and
disperse in water. Dispersive soils are devastating to plant life because
they limit the free exchange of air and infiltration of water (American
Petroleum Institute, 1989b).
The sodium adsorption ratio (SAR) is an empirical mathematical
expression used to characterize the detrimental effects of sodium on
soils. It is calculated through the following equation:
The Impact of Drilling and Production Operations
99
Na+
SAR =
Mg2+
where the cation concentrations are expressed in millimoles/liter.
Concentrations are determined by direct chemical analysis of reserves
pit liquids or aqueous extracts of waste solids or soils. High sodium
levels (SAR greater than 12) in soil solutions cause Ca and Mg
deficiencies in plants (American Petroleum Institute, 1989b).
3.3.2 Impact on Aquatic Organisms
Most, but not all, produced waters have a salt content higher than
that found in the local ecosystems. The discharge of water having a
higher salt content can impact aquatic organisms. High concentrations
of sodium chloride can affect the development of embryos and fetuses
and can cause fetal death. High salt concentrations can also affect the
development of the musculoskeletal system and cause eye, skin, and
upper respiratory system irritation.
Bioassay tests have been conducted with brines to determine the
toxicity of various salts to aquatic organisms. Common freshwater
species used for these tests include the water flea, rainbow trout, and
the fathead minnow. As seen in Table 37, 48hr LC50 values for the
Table 3-7
Toxicity of Salts to Water Flea, 48-hr LC50 (mg/L)
Salt
Anion
Cation
Total
KC1
K2S04
KHCO,
NaCl
Na2S04
NaHCO3
CaCI2
CaSO4
MgCl7
MgSO4
270
400
300
1,300
2,500
740
1,200
1,430
730
1,400
290
330
200
840
1,260
260
700
600
250
360
560
730
500
2,140
3,760
1,000
1,900
2,030
980
1,760
Source: after Mount et ai, 1993,
Copyright SPE, with permission.
100
Environmental Control in Petroleum Engineering
water flea for a variety of pure salts are on the order of 1,000 mg/1
(Mount et al., 1993). Studies indicate that a concentration of 230 mg/1
for total dissolved solids may be sufficient to protect warm water
species in natural streams. No significant change in macro invertebrate
behavior was observed below a level of 565 mg/1 (Vickers, 1990).
Because the salinity of many produced waters is greater than that
of marine waters, the environmental impact of high salt concentrations is
also of concern regarding marine organisms. Highly saline water has a
higher density than seawater and will segregate to the bottom of any
surface waters. This density gradient inhibits the mixing and dilution
of the very salty water. This segregation is only a problem in shallow
estuaries and marshes that allow little dilution (St. Pe et al,, 1990).
The impact of a saline brine spill in a saltwater marsh was observed
in 1989 following a spill of about 35 million gallons of brine (Bozzo
et al., 1990). The salinity of the brine varied between 0 and 274 parts
per thousand (ppt), with 17 million gallons having a salinity over 220
ppt. In comparison, seawater has a salinity of 35 ppt. Following the
spill, vegetation in areas with poor drainage and along drainage
channels was completely killed. Flushing from rainwater, turbulent
mixing from nearby barge traffic, and tidal events lowered the salinity
in the soils around the spill to ambient levels within a few months.
Salttolerant plants began growing in the areas where the salt had
killed the less tolerant plants. The following year, vegetation in all
areas except those most severely affected showed signs of recovery,
3.4
HEAVY METALS
The heavy metals encountered in drilling and production activities
are related to a variety of environmental concerns, depending on the
metal and its concentration. At very low concentrations, some metals
are essential to healthy cellular activity. Essential metals include
chromium, cobalt, copper, iodine, iron, manganese, molybdenum,
nickel, selenium, silicon, vanadium, and zinc (Valkovic, 1978). At high
concentrations, however, metals can be toxic. Because most concentra
tions encountered during drilling and production are relatively low, the
environmental impact is generally observed only after chronic exposure.
The environmental impact of heavy metals is manifested primarily
through their interaction with enzymes in animal cells. Enzymes are
complex proteins that catalyze specific biochemical reactions. Heavy
The Impact of Drilling and Production Operations
101
metals affect the action of enzymes. Excess concentrations of metals
inhibit normal biochemical processes in cells. This inhibition can result
in damage to the liver, kidney, or reproductive, blood forming,
or nervous systems. These effects may also include mutations or
tumors. Many metals can impact embryo and larval states of fish and
benthic invertebrates.
The toxicities of many metals found in the upstream petroleum
industry have been summarized by the American Conference of Govern
mental Industrial Hygienists (ACGIH) and are listed in Table 38
(Proctor et al., 1989). This table lists the threshold limit values (TLV)
for airborne exposures.
The toxicity of trace metals in agricultural soils is summarized by
Logan and Traina (1993) and is given in Table 39. This table identifies
whether the element is essential, beneficial, or toxic to plants and
animals. Also found is a typical concentration of each metal in soils,
From this table it can be seen that many metals are essential in low
concentrations, but toxic in high concentrations.
A description of the health impacts of a number of heavy metals is
given below. Further information about these and other metals is
available in the literature, for example, Valkovic (1978), Proctor et al.
Table 3-8
Concentration Limits for Heavy Metals
Metal
Aluminum
Arsenic
Barium (soluble compounds)
Barium (barium sulfate)
Cadmium
Chromium (trivalent)
Chromium (hexavalent)
Lead
Mercury
Nickel (soluble inorganic compounds)
Vanadium (as vanadium pentoxide)
Zinc (as zinc oxide)
Source: Proctor et al., 1989.
Copyright Van Nostrand Reinhold, with permission.
TLV (mg/m3)
2.0
0.2
0.5
10
0.05
0.5
0.05
0.15
0.05
0.1
0.05
5
102
Environmental Control in Petroleum Engineering
Table 3-9
Role of Trace Metals in Plants and Animals
Metal
Toxic
Toxic
Essential Beneficial
to
Animals
to Plants to Animals to Plants
Antimony
Arsenic
Barium
Beryllium
Bismuth
Boron
Cadmium
Chromium
Cobalt
Copper
Lead
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silver
Tin
Tungsten
Vanadium
Zinc
No
No
No
No
No
Yes
No
No
Yes
Yes
No
Yes
No
Yes
Possible
Yes
No
No
No
Yes
Yes
No
Yes
Possible
No
No
No
No
Yes
Yes
Yes
No
Yes
No
Yes
Yes
Yes
No
Yes
No
Yes
Yes
9
Yes
Low
Yes
Yes
Yes
Yes
Yes
Low
Yes
Yes
Yes
No
Yes
Yes
Yes
No
'?
9
Yes
Yes
Yes
Yes
Low
Yes
Yes
_
Yes
Yes (Cr6+)
Low
Yes
Yes
Low
Yes
Yes
Yes
Yes
Yes
Yes
?
Yes
Yes
Typical
Concentration
(mg/kg)
1.5
7
500
2
0.2
20
0.35
75
9
22
25
700
0.07
1.5
30
0.3
0.05
4
1.5
75
60
Source: adapted from Logan and Traina, 1993.
Reprinted from Metals in Groundwater, with permission. Copyright Lewis Publishers, an
mprint of CRC Press, Boca Raton, Florida.
(1989), Calabrese and Kenyon (1991), St. Pe et al. (1990), and the
American Petroleum Institute (1981b).
Antimony: Inhalation can cause dermatitis, keratitis, conjunctivitis, and
nasal septum ulceration. Amounts greater than about 0.1 g are considered
o be lethal to humans by ingestion. Antimony shortens lifespan when fed
o rats and mice. It also causes phenmonitis and heart and liver damage.
Arsenic: Chronic exposure to arsenic can lead to weakness, anorexia,
bronchitis, gastrointestinal disturbances, peripheral neuropathy, skin
The Impact of Drilling and Production Operations
103
disorders, and damage to the liver, heart, nerves, and kidneys. Expo
sure to arsenic compounds in drugs, food, and water have been
causally associated with the development of cancer, primarily of the
skin and lungs, although a direct connection has never been proven,
Low doses stimulates plant growth. Arsenic may impact embryo and
larval states of fish and benthic invertebrates.
Barium: Barium ion is a muscle poison causing stimulation and then
paralysis. Soluble barium salts are skin and mucous membrane irri
tants. In animals, BaO and BaCO3 cause paralysis. Ba is also poisonous
to most plants. The barium ion is a physical antagonist of potassium,
interfering with the vital cellular use of potassium.
Although elemental barium is extremely toxic, the barium com
pounds encountered during drilling and production activities are
relatively nontoxic. The most commonly found form of barium is
barium sulfate, which is insoluble in geochemical conditions and is
not taken up by plants. Barium sulfate is not absorbed by animals or
humans if ingested. It is commonly used internally for medical applica
tions using Xray diagnostics. Barium carbonate is moderately soluble
and is more toxic, but is rarely used.
Cadmium: Excess exposure to cadmium can lead to renal failure,
anemia, bone fractures, kidney stones, osteomalacia, retarded growth,
pulmonary emphysema, and pain in the back and joints. Cadmium has
been implicated in respiratory tract cancer. There is little evidence of
carcinogenicity for exposure by ingestion. Organometallic derivatives
may be concentrated in lipid tissues and cause chromosome damage.
Cadmium interferes with the metabolism of zinc and copper in humans,
Chromium: The toxicity of chromium depends primarily on its chemi
cal valence state and its concentration. Chromium is considered to be
an essential element in humans at low levels. At higher concentrations,
hexavalent chromium can be highly toxic, while trivalent chromium
is relatively nontoxic. Hexavalent chromium can cause severe irritation
to the respiratory system, asthma, and kidney damage. Some hexa
valent chromium compounds are carcinogenic. Prolonged inhalation
of trivalent chromium may cause scarring of the lungs. Other effects
of chronic exposure at high levels include lung cancer, dermatitis,
alceration of the skin, chronic catarrh, and emphysema. However,
104
Environmental Control in Petroleum Engineering
virtually all chromium found in the drilling and production industry
s in the low solubility, low toxicity trivalent form.
Bioassays on freshwater organisms for trivalent chromium at con
centrations around 1.0 mg/1 yielded a mixture of no effects to mixed
sublethal effects after exposures of up to three months. A threeweek
LC50 value for Daphnia magna (freshwater shrimp) was reported as
2.0 mg/1. No significant mortalities were observed on Neanthes arenaceodentata (marine polychaetes) for threeweek exposures to trivalent
chromium at concentrations up to 12.5 mg/1. Bioassays on marine
organisms for trivalent chromium yielded 96hr LC50 values of 53 mg/1
on juvenile fish and 24hr LC100 values (100% mortality) of around
50 mg/1 on invertebrates. For comparison, 96hr LC50 values on the
same invertebrate species for hexavalent chromium was about 3.0 mg/1
(American Petroleum Institute, 1981b),
Cobalt: This metal is essential to bluegreen algae and some bacteria,
fungi, and green algae, but there is little evidence of its essentiality
o higher plants. Normal human intake is 0.002 mg/day, with toxic
evels at 500 mg/day. Cobalt metal dust is more toxic than salts in
inhalation. Higher concentrations cause dermatitis, heart and gastro
ntestinal tract disorders, and liver and kidney damage.
Copper: Inhalation of dust causes lung and gastrointestinal disturbances.
It affects erythrocytes and the liver and irritates skin and mucous membranes,
Lead: Prolonged exposure induces toxic responses in the hemotologi
cal, neurological, and renal systems, leading to brain damage, convul
sions, behavioral disorders, and death. There is some evidence that
some soluble lead salts are carcinogenic in some animals, but there
s little evidence of their carcinogenicity in humans. Organometallic
derivatives may be concentrated in lipid tissues and cause chromosome
damage. Some plants show retarded growth at 10 ppm. Subtoxic
effects have been observed in microflora at 0.1 ppm.
Manganese: Pathological effects on nerve cells and the liver have
been reported.
Mercury: Chronic exposure to mercury causes weakness, fatigue,
anorexia, and disturbances of gastrointestinal functions. Following high
The Impact of Drilling and Production Operations
105
exposures, tremors and spasms of the fingers, eyelids, lips, and even
the whole body can occur. In severe cases, delirium and hallucinations
may occur. Mercury exposure can damage the nervous system, kid
neys, and liver. There is no evidence of mercury being carcinogenic
in humans. Organometallic derivatives may be concentrated in lipid
tissues and cause chromosome damage. Subtoxic effects have been
observed in microflora at 0.1 ppm. Detrimental effects have been
observed in aquatic ecosystems at 0.005 ppm.
Nickel: Exposure to nickel can cause a sensitization of the skin and
allergic reactions in the respiratory tract. It has been associated with
nasal and lung cancer, but carcinogenicity from ingestion has not been
proven. The carcinogenicity of nickel compounds appears to depend
on the solubility of the compounds. Organometallic derivatives may
be concentrated in lipid tissues and cause chromosome damage,
Vanadium: Exposure from inhalation affects the eyes and respiratory
system. At high exposure levels, damage to the lungs, liver, kidneys,
and heart have been observed. No evidence of carcinogenicity has
been observed,
Zinc: Inhalation of zinc oxide causes an influenzalike illness. Moder
ate exposures have little adverse effects on the lungs. No evidence has
been obtained suggesting that zinc compounds are carcinogenic. Zinc
is an essential element in the human metabolism and is required in
low concentrations. It is toxic to plants above 400 ppm and lethal to
fish and other aquatic animals at 1.0 ppm.
3.5 PRODUCTION CHEMICALS
The various chemicals used during production have a widely vary
ing potential for environmental impact, depending on the chemical and
its concentration.
The environmental impact of acids varies somewhat with acid
type. AH acids can be corrosive to eyes and skin. Hydrofluoric acid
can be lethal if sufficient quantities are absorbed through the skin,
inhaled, or ingested. Effects from chronic exposure to hydrofluoric acid
include fluorosis (fluoride poisoning) and kidney or liver damage.
Chronic exposure to hydrochloric acid can cause irritation to mucous
106
Environmental Control in Petroleum Engineering
membranes, erosion of teeth, and aggravation of respiratory conditions
such as asthma. Little aquatic toxicity data are available for acids.
Pesticides vary in toxicity. Prolonged or repeated exposure may
cause various systemic effects, including damage to the nervous and
muscular systems. Some pesticides are carcinogenic. Exposure to some
pesticides can be fatal.
Glycol can be fatal if ingested in quantities of about 100 ml. Lower
doses may be irritating to the mouth, throat, and stomach and can
cause disorders of or damage to the digestive tract. Repeated exposure
can cause kidney, brain, or liver damage. Blood chemistry and blood
cells can also be affected.
Bioassays have been conducted for a variety of production chemi
cals using different freshwater and saltwater organisms. Table 310
summarizes the typical concentrations of some chemicals used for
different types of applications. This information includes typical ranges
of chemical concentrations when used, concentrations when discharged
for disposal, and the LC50 values (Hudgins, 1992). From this table, it
can be seen that the toxicities of production chemicals vary widely.
More detailed toxicity data are summarized for scale inhibitors in
Table 311, for biocides in Tables 312a and 312b, reverse emulsion
breakers in Table 313, emulsion breakers in Table 314, corrosion
inhibitors in Table 315, paraffin inhibitors in Table 316, surfactants
in Tables 317a through 317e, coagulants in Table 318, foam breakers
in Table 319, and gas treatment chemicals in Table 320. Because of
varying test protocols, a direct comparison of the toxicities of these
chemicals may not be valid.
3.6 DRILLING FLUIDS
Two methods have been used to evaluate the environmental impact
of drilling fluids. First are bioassays conducted using various organ
isms placed in different concentrations of drilling fluids. Second are
direct measurements of environmental impact following disposal of
drilling fluids, either in reserves pits or by offshore dumping.
3.6.1
Bioassays of Drilling Fluids
Bioassays using mysid shrimp (Mysidopsis bahia) are currently
required for the offshore discharge of drilling fluids in the United
The Impact of Drilling and Production Operations
107
Table 3-10
Toxicity of Production Chemicals
Typical
Concentration
During Usage
(ppm)
Typical
Concentration
as Discharged
(ppm)
Scale inhibitor
310'
310
Biocides
5,0002
1050'
50500
1050
1002003
125'
100200
0.5–12
505
0.4–4
10204
515
10–205
2–5
,<. *j
Paraffin inhibitors
5,0002
50300
25100
0.53
Surfactant cleaners
—
Chemical
Application
Reverse emulsion breakers
Emulsion breakers
Corrosion inhibitors
—
LC50
(ppm)
l,200> 12,000
90%>3,000
0.2> 1,000
90%>5
0.215,000
90%>5
4–40
90%>5
0.25
90%>1
21,000
90%>5
1.544
90%>3
0.5429
90%>5
'Concentration during continuous operation.
Maximum concentration in returns after batch job,
3
Maximum concentration of slug.
4
Water-soluble chemical.
5
Oil-s0luble chemical.
Source: from Hudgins, 1992.
Copyright SPE, with permission.
States (Ayers et al., 1985). In this test, the drilling fluids are first
mixed with seawater at a ratio of one part drilling mud to nine parts
seawater. The pH of the solution is adjusted to that near seawater (7.8–
9.0) by adding acetic acid. The mixture is stirred for five minutes and
allowed to settle for one hour. A portion of the fluid is filtered through
(text continued on page 114)
108
Environmental Control in Petroleum Engineering
Table 3-11
Acute Toxicity of Scale Inhibitors (96-hr LC50, mg/L)
Generic Chemical Type
Fresh Water
Salt Water
Amine phosphate ester
Phosphonate
>1,000
3,700>10,125
>4,309
1,676>10,125
Source: after Hudgins, 1992.
Copyright SPE, with permission.
Generic Type
Table 3-12a
Acute Toxicity of Biocides (LC50, mg/L)
Generic Chemical Type
Fresh Water
Salt Water
Aldehydes
Glutaraldehyde (25%)
Glutaraldehyde (50%)
Formaldehyde
16.943
11.523.7
18–64
2.11,100
—
231,000
Formaldehyde
mixtures
With heterocyclic polyamine
With alkyldimethyl
benzyl quaternary
41.473.3
2.91,000
1.792.24
12290
Quaternary
Ethoxy quaternary
Dicocoamine
0.351.32
0.421.7
174–1,000
0.434
Amine salt
Cocodiamine acetate
Cocodiamine fatty acids
Others
0.221.6
0.730.92
0.091.62
0.719–965
0.22670
24922
Amine
Alkyl propylene
diamine+ 2 ethylhexanol
0.750.78
0.49–49
>100
180
4.58.15
1.29
40.6
0.861.26
0.0360.042
2.8> 1,000
1.38
66.14,000
—
Others
Metronidazole
2,2dibromo
3nitrilopropionamide
Dithiocarbamates
Isothiazalin
2,4,5trichlorophenate
Toxaphene pesticide
Test lengths are for either 48 or 96 hours.
Source: after Hudgins, 1992.
Copyright SPE, with permission.
The Impact of Drilling and Production Operations
109
Table 3-12b
Toxicity of Biocides (15-minute microtox, EC50, mg/L)
Biocide
Ammonium bisulfate
Chlorinated aromatic
Fatty diamine
Formulated fatty diamine
oxygen scavenger mixture
Fatty amine
Polymeric biguanide hydrochloride
Organobromide
Pure
With Oxygen
Scavenger
250500
0.33
3.9
—
0.52
1.6
—
3.7
1.1
2.5
2.4
1.1
1 .5
33
Source: after Whale and Whitham, 1991.
Copyright SPE, with permission.
Table 3-13
Toxicity of Reverse Emulsion Breakers (96-hr LC50, mg/L)
Generic Chemical Type
Cationic polyelectrolyte + metal salts
Polyamine ester + zinc salt
Polyacrylate
Cationic polyelectrolyte
Fresh Water
Salt Water
1.24.4
56
2351,020
13,46715,621
> 1,000
—
16,713
1.2–4.4
Source: after Hudgins, 1992.
Copyright SPE, with permission.
Table 3-14
Toxicity of Emulsion Breakers (96-hr LC50, mg/L)
Generic Chemical Type
Oxyalkylated dopropylene glycol
Phenol formaldehydes
Alkyl aryl sulfonate
Source: after Hudgins, 1992.
Copyright SPE, with permission.
Fresh Water
Salt Water
40
5.2625.4
6.77.5
3.5628
10
110
Environmental Control in Petroleum Engineering
Table 3-15
Toxicity of Corrosion Inhibitors (96-hr LC50, mg/L)
Generic Chemical Type
Amide/imadizoline
Amide/imadizoline + quaternary
Quaternary
Ammonium salts
Amines
Sulfonate
Phenanthradine
Pyridine salt + quaternary
Alkyl morpholines
Ammonium bisulfite
Sodium sulfite
Fresh Water
Salt Water
0.2675
1.21.3
1,52.8
2,1226!
15
0,86
5.96116
1.98710
220
6.1
2,26
75423
7,000
800–1,055
77–788
Source: after Hudgins, 1992.
Copyright SPE, with permission.
Table 3-16
Acute Toxicity of Paraffin Inhibitors (96-hr LC50, mg/L)
Generic Chemical Type
Vinyl polymer
Sulfonate salt
Alkyl polyether + aryl polyether
Other
Source: after Hudgins, 1992.
Copyright SPE, with permission.
Fresh Water
Salt Water
42
1725.1
2.7
37.4
1.55
13.337.4
1744
The Impact of Drilling and Production Operations
111
Table 3-17a
Toxicity of Surfactant Cleaners (96-hr LC50, mg/L)
Generic Chemical Type
Fresh Water
Salt Water
3.5192
48106
0.5
183
5.6429
56410
40
Oxyalkylate
Alkoxylated phenol
Cationic (quaternary)
Giycol ether
—
Source: after Hudgins, 1992.
Copyright SPE, with permission.
Table 3-17b
Toxicity of Nonionic Surfactants (96-hr LC50, mg/L)
Test Species
Surfactant Type
Fatty alcohol ethoxylates
(C I2 C l5 )
Fatty alcohol ethoxylates
(C,0CI2)
Fatty alcohol ethoxylates (C )
Disecbutylphenol ethoxylate
Polypropylene glycols
(MW=4,000)
Polypropylene glycols
(MW=400)
Ethoxylated alkyl
alcohols + methanol
Ethoxylated alkyl
alcohols + isopropanol
Unspecified surfactant
Source: after Maddin, 1991.
Copyright SPE, with permission.
Toxicity
Pimephales promelas
<3
Pimephales promelas
64
Pleuronectes platessa
Crangon crangon
Algae
Pimephales promelas
Pholis gunnellus
Gasterosteus aculeatus
Crangon crangon
Chaetogammarus marinus
Pimephales promelas
Pimephales promelas
7.5
22
5
20
90
90
180
49
50
> 100
Pimephales promelas
>100
Crangon crangon
33100
Crangon crangon
100330
Fish
1040
112
Environmental Control in Petroleum Engineering
Table 3-17c
Toxicity of Anionic Surfactants (96-hr LC50, mg/L)
Test Species
Surfactant Type
Dodecylbenzenesulfonic acid
with disecbutylphenol ethoxylate
Dodecyclbenzenesulfonic acid
Sodium dodecylbenzenesulfonate
Sodium tetrapropylbenzenesulfonate
Sodium alkyl(branched) benzenesulfonate
Sodium alkyl(C10C15) benzenesulfonate
Disodium decyldiphenylether
disulfonate
Sodium polynaphthalenesulfonate
Ammonium decyl
poly ethoxy ether sulfate
Sodium dodecylethoxyether sulfate
Sodium palmitate
Sodium oleate
Sodium stearate
Gasterosteus aculeatus
Crangon crangon
Fish
Salmo gairdneri
Cyprinus carpio
Salmo gairdneri
Cyprinus carpio
Cyprinus carpio
Salmo gairdneri
Pimephales promelas
Pimephales promelas
Salmo gairdneri
Fish
Fish
Fish
Fish
Toxicity
0,32
3301,000
<10
4_6
46
12
12
18
1.9
4
375
140
<10
1012
10–12
10–12
ource: after Maddin, 1991.
Copyright SPE, with permission.
Table 3-17d
Toxicity of Cationic Surfactants (96-hr LC50, mg/L)
Surfactant Type
Alkyl (C8CI8) di(2hydroxyethyl)
benzyl ammonium chloride
Octadecyldimethyl ammonium chloride
Unspecified biocides
Perfluorooctylsulfonamidopropyltrimethyl
ammonium iodide
Dodecyltrimethyl ammonium chloride
with dodecyldiethanolamine oxide
ource: after Maddin, 1991.
Copyright SPE, with permission.
Test Species
Salmo gairdneri
Salmo gairdneri
Crangon crangon
Pimephales promelas
Toxicity
5,4
4
0.2> 1,000
30
55
The Impact of Drilling and Production Operations
113
Table 3-17e
Toxicity of Amphoteric Surfactants (96-hr LC50, mg/L)
Surfactant Type
Dodecylbetaine
Dodecylbetanie with
polypropylene glycol
(MW=400)
Test Species
Toxicity
Pimephales promelas
12
Pimephales promelas
Daphnia magna
87
11
Source: after Maddin, 1991.
Copyright SPE, with permission.
Table 3-18
Toxicity of Coagulants (96-hr LC50, mg/L)
Generic Chemical Type
Polyamine ester
Polyacrylamide
Phosphate ester
Polyamine quaternary
Polyquaternary
Salt Water
Fresh Water
> 1,000
14,800
1,800
0.240.52
498
21
Source: after Hudgins, 1992.
Copyright SPE, with permission.
Table 3-19
Acute Toxicity of Foam Breakers (96-hr LC50, mg/L)
Generic Chemical Type
Alcohol modified fatty acid
Trybutyl phosphate
Source: after Hudgins, 1992.
Copyright SPE, with permission.
Fresh Water
50
Salt Water
114
Environmental Control in Petroleum Engineering
Table 3-20
Toxicity of Gas Treatment Chemicals (96-hr LC50, mg/L)
Chemical
Methanol
Ethylene glycol
Diethylene glycol
Triethylene glycol
Fresh Water
Salt Water
8,000> 10,000'
> 10,000
>5,000~>32,0002
> 10,00062,600
12,00028,000
>20,000'
>1,000J
48-hour text
24-hour test
23-dav test
Source: after Hudgins, 1992.
Copyright SPE, with permission.
text continued from page 107)
a 0.45 micron filter and designated the "liquid phase." The remaining
unfiltered fluid is designated the "suspended particulate phase." The
settled material at the bottom of the mixing vessel is called the "solid
phase." Chemical additives, if any, are then mixed with this liquid for
he toxicity test.
Mysid shrimp are used as the test organisms for the liquid and sus
pended particulate phases, while hardshell clams are used for the solid
phase. The U.S. Environmental Protection Agency has set a mysid shrimp
oxicity limit (96hour LC50) for drilling mud discharge into the United
States outer continental shelf (OCS) waters of 30,000 ppm (3%) for
suspended particulate phase (after the 9:1 dilution with sea water).
Materials with LC50 values greater than one million ppm do not kill
at least one half of the mysid shrimp during the 96hour test.
Testing drilling fluids for toxicity in aquatic systems is difficult,
however, because much of the material settles rapidly, and what
remains suspended may partition into two or three discrete layers. This
makes repeatability of the exact test conditions difficult. The condition
of the test animals prior to exposure to the drilling fluids is also an
mportant factor in determining the test repeatability. Laboratory tests,
however, have shown similar results from different labs for the toxicity
of various materials in drilling fluids (Parrish and Duke, 1988).
To speed permitting of new offshore wells and eliminate the need
or bioassays on every drilling fluid prior to discharge, a set of eight
generic drilling muds were developed for offshore use in the United
The Impact of Drilling and Production Operations
115
States (Ayers et al., 1985; Arscott, 1989). These muds have been
approved for use in specific regions without bioassay testing every
time a mud is to be discharged. Special chemical additives like lost
circulation materials and lubricants can also be used if they come from
an approved additive list. The discharge of diesel or free oil is not
permitted under the generic mud program, although cuttings contami
nated with oil can be discharged if they are washed and do not cause
a sheen. If generic muds are not used, permits must be obtained on a
wellbywell basis under the National Pollutant Discharge Elimination
System. (NPDES).
A number of bioassay studies have been conducted to determine the
toxicity of various drilling muds and their additives. Two sets of
toxicity data for these generic muds are given in Tables 3.2la and 3.2Ib.
From these tables, it can be seen that the generic muds generally pass
the 30,000 ppm toxicity limit on the liquid phase. The 95% confidence
limit on the measured LC50 toxicities from one set of mysid shrimp
bioassays has been reported to be about 30% of the measured value
(Parrish et al., 1989). Toxicity data from several nongeneric muds are
given in Table 322. From this table, it can be seen that muds that
Table 321 a
Toxicity of Generic Drilling Muds (96hr LC50, ppm)
Generic Mud Type
Liquid Phase
Toxicity1
Suspended
Particulate Phase
Toxicity1
58,00066,000
Potassium chloride polymer
25,00070,900
Lignosulfonate seawater
283,500880,000
53,200870,000
Lime
66,000860,000
393, 000> 1,000,000
Nondispersed
> 1,000,000
> 1,000,000
Spud mud (slugged
intermittently with seawater)
> 1,000,000
> 1,000,000
Seawater/freshwater gel
> 1,000,000
> 1,000,000
Lightly treated lignosulfonate
freshwater/seawater
> 1,000,000
> 1,000,000
Lignosulfonate freshwater
> 1,000,000
506,000> 1,000,000
''Mysid shrimp
Source: from Ayers et al., 1985.
Copyright SPE, with permission.
116
Environmental Control in Petroleum Engineering
Table 3-21 b
Toxicity of Generic Drilling Muds (96-hr LC50, ppm)
Generic Mud Type
Potassium chloride polymer
Lignosulfonate seawater
Lime
Nondispersed
Spud mud (slugged intermittently with seawater)
Seawater/freshwater gel
Lightly treated lignosulfonate freshwater/seawater
Lignosulfonate freshwater
Liquid Phase Toxicity'
27,000
516,000
163,000
> 1,000,000
> 1,000,000
> 1,000,000
654,000
293,000
Mysid shrimp
Source: from Arscott, 1989.
Copyright SPE, with permission.
Table 3-22
Mysid Shrimp Toxicity of Drilling Mud Additives
Mud Type
Potassium chloride polymer (generic #1)
Lignosulfonate seawater (generic #2)
Lime (generic #3)
Lignosulfonate freshwater (generic #8)
PHPA 9.6 Ibm/gal
PHPA 14.3 Ibm/gal
PHPA/20% NACL/14.5 Ibm/gal
PHPA seawater 13.5 Ibm/gal
Cationic Mud
Freshwater chromelignosulfonate+2% diesel
Freshwater chromelignosulfonate+2% mineral oil
(15% aromatics)
Freshwater chromelignosulfonate+2% mineral oil
(0% aromatics)
Mineral oil
ource: from Wojtanowicz, 1991.
Copyright SPE/IADC, with permission.
96-hr LC50 (ppm)
33,000
621,000
203,000
300,000
> 1,000,000
> 1,000,000
140,000
> 1,000,000
> 1,000,000
5,970
4,740
22,500
180,000
The Impact of Drilling and Production Operations
117
contain chrome lignosulfonate and oil may fail the 30,000 ppm require
ment for offshore discharge. Bioassay on many commercial drilling
fluid additives have also been conducted (Offshore, 199la and 199Ib).
Oilbased muds using diesel are more toxic than those using mineral
oils. Studies have shown that the toxicity of mineral oils can be 5 to
14 times lower than diesel (Wojtanowicz, 1991), The mechanisms of
toxicity reduction has been attributed to a reduced content of aromatic
hydrocarbons in mineral oils and a low water solubility of the toxic
components that are present, Diesel oil typically has between 30% and
60% aromatic compounds, while some mineral oils have virtually no
aromatic compounds.
Conklin and Rao (1984) reported that the toxicity of whole drilling
fluid on grass shrimp varies significantly with its formulation. The
addition of diesel oil to the drilling fluids at a level of 0,9% increased
the toxicity to grass shrimp by a factor of about 200, while the addition
of mineral oil at the same concentration increased toxicity by a factor
of about 50.
One of the difficulties with conducting bioassays on drilling muds
is that new additives and formulations are continually being developed.
The high cost of bioassays makes it difficult to justify bioassays on
all conceivable combinations of additives and formulations. One
approach that has been suggested to minimize the number of bioassays
conducted is to measure the toxicity of the individual additives
and then use an appropriate mathematical model to estimate the
toxicity of their combinations. One mathematical model that has been
proposed is to add the mass weighted reciprocals of the LC50 values
of all constituents.
!
LC,,
=
v xi
" ^LC
(3-5)
where x. is the mass fraction of the i component. Toxicity measure
ments on additives and their combinations have shown that this model
results in calculated LC50 values for mixtures that are significantly
lower than those measured, i.e., the mixture is less toxic than predicted
by this formula (Parrish et al., 1989).
Drilling fluids can have significant sublethal effects on marine
organisms. Parrish and Duke (1990) have summarized the work of a
118
Environmental Control in Petroleum Engineering
number of studies in this area. Sublethal effects of ferrochrome
lignosulfonate were observed on corals at levels of 0.1 ml/1 of used
drilling fluid in sea water. Lobsters were observed to have an inhibited
response to food odors at drilling fluid concentrations as low as 0.01
mg/1, and lethality (96hr LD50) was observed for lobster larvae at
concentrations between 0.074 and 0.5 ml/1 for various drilling fluids.
Behavioral changes, including delays in feeding, molting, and shelter
construction, were observed at levels as low as 0.007 mg/1. Drilling
fluid concentrations between 1 and 10 mg/1 adversely effected fertiliza
tion and subsequent embryo development of estuarine minnows; but
the concentration where an effect was observed varied significantly
with the particular drilling fluid tested. Sea urchins showed reduced
fertilization rates when exposed to 223 mg/1 barium sulfate. Behavioral
characteristics, such as foraging by fish, gaping by scallops, and
burrowing by shrimp, however, were unaffected by what was con
sidered a realistic deposition rate on the sea floor within a 50meter
radius of a drilling platform.
Some accumulation of barium and chromium from the solids portion
of used lignosulfonate drilling fluids has been observed in some
benthic (sea bottom dwelling) species following exposure (American
Petroleum Institute, 1985d). Some sublethal impacts were observed that
included alterations in biochemical composition, depletion of micro
nutrients, and altered respiration and excretion rates. Once contaminated
animals were placed in a clean environment, however, the concentrations
in the animals was reduced to nominal levels. In other species, how
ever, there were no observed bioaccumulation or effects.
The concentrations of drilling fluids that had no observable effect
on the development of embryos of estuarine minnows (Fundulus
heteroclitus), sand dollars (Echinarachnius parma) and sea urchins
(Strongylocentrotus purpuratus, Lytechinus pictus, and L. variegatus)
were measured by the U.S. Environmental Protection Agency (1983),
Fish embryos were placed in the liquid phase of drilling fluids one
minute after fertilization and maintained for the duration of their
development. Sand dollar and sea urchin embryos were placed in the
test medium 1015 minutes after fertilization and kept there for 96
hours. The "safe" concentration—the concentration that is 10% of the
lowest concentration that had an observable effect—was measured and
is reported in Table 323. These safe concentrations were typically 1
100 microliters per liter.
The Impact of Drilling and Production Operations
119
Table 3-23
Toxicity of Drilling Fluids to Hard Clams, EC50
Drilling Fluid Type1
Concentration (micro!/!)
Seawater lignosulfonate
Seawater lignosulfonate
Seawater lignosulfonate
Lightly treated lignosulfonate
Freshwater lignosulfonate
Lime
Freshwater lignosulfonate
Freshwater/ seawater lignosulfonate
Reference drilling fluid
1
Duplicate drilling fluid types are from different
100
1
10
10
100
10
100
100
1
formulations.
Source: U.S. Environmental Protection Agency, 1983.
3.6.2
Impact of Drilling Fluid Disposal
Drilling fluids used for onshore wells are primarily disposed of in
reserves pits, while in many areas drilling fluids from offshore plat
forms have been dumped overboard. A number of studies have been
conducted on the impact of these discharges.
For most drilling muds, sodium has the greatest potential to impact
the environment from the onshore disposal in reserves pits (Miller,
1978). Heavy metals are also of concern, although their potential to
leach away from the pit and contaminate the groundwater is limited
by their low concentration and low solubility (Mosley, 1983; Branch
et al., 1990; Crawley and Branch, 1990; Candler et al., 1990; American
Petroleum Institute, 1983). Extensive field studies have suggested that
the onshore disposal of drilling wastes in reserves pits poses no serious
threat to human health or the environment (American Petroleum
Institute, 1983). In some cases, crop yield was improved following the
disposal of drilling wastes.
A number of field studies have been conducted to measure the
mpact of discharging drilling fluids on the benthic community around
offshore platforms. These studies have revealed elevated levels of
hydrocarbons and heavy metals in the sediments surrounding plat
forms. Most of these hydrocarbons and heavy metals are associated
with cuttings, making it possible to estimate the deposition of these
120
Environmental Control in Petroleum Engineering
materials by modeling the deposition of the cuttings. Models for
sediment deposition following discharge from offshore platforms are
available (MacFarlane and Nguyen, 1991).
In one study, the heaviest accumulations of hydrocarbons and
heavy metals were found to be within about 100 meters of the plat
forms, with lower accumulations at farther distances (American Petrol
eum Institute, 1989c). The impact of these accumulations on the
benthic community was uncertain. Seasonal variations in the organic
matter content from nearby river runoff was greater than the concen
trations from the platform. Seasonal variations in the benthic com
munity were also greater than those observed at varying distances from
the platform.
The greatest impact of offshore discharge of drilling fluids is when
oilbased muds are used. Elevated hydrocarbon levels in the sediments
and impacts on the benthic community have been measured at dis
tances of several kilometers from platforms (Bakke et al., 1990;
Peresich et al., 1991). The hydrocarbon concentration in the sediments,
however, decreased significantly over a period of several years follow
ing discharge. The distance away from a platform that elevated levels
of hydrocarbons can be detected may also depend on whether the
cuttings were washed prior to discharge (De Jong et al., 199la). The
threshold level of hydrocarbons in subsea sediments below which no
effects were observed on the mortality of the heart urchin (Echinocardium ordatum) was determined to be on the order of 10–100 mg
oil/kg sediment (De Jong et al., 1991b). Because of these effects, the
discharge of oilbased muds and their associated cuttings is prohibited
in many areas around the world.
3,7 PRODUCED WATER
The potential for environmental impact following the discharge of
produced water arises primarily from its high salt content, its heavy
metals content, its dissolved or suspended hydrocarbons, and its
oxygen deficiency.
The acute toxicity of a selection of produced waters to mysid shrimp
(96hr LC50) was found to range between 1.3% to 9.3% by volume of
produced water in seawater (U.S. Environmental Protection Agency,
1989). Sublethal effects were observed for produced water concentra
tions as low as 0.5% after 19 days of exposure. The toxicity of the
The Impact of Drilling and Production Operations
121
produced water could not be correlated with total volatile organic
carbon, total organic carbon, oil and grease, or salinity.
Field studies around offshore platforms have shown that the impact
of produced water discharge depends on the volume of water dis
charged and the water depth. Except for shallow waters, little effect
on the benthic community has been observed at distances greater than
about 100 meters from the platform (American Petroleum Institute,
1989d; Rabalais et al., 1990).
Onshore discharges of produced water may be allowed if the water
has a "beneficial use" in agriculture and wildlife propagation, even if
t is not suited for human use. In Wyoming, for example, acceptable
water quality is determined if more than 50% of water fleas and
athead minnows can survive in the produced water for 48 and 96
hours, respectively (Mancini and Stilwell, 1992).
3.8 NUCLEAR RADIATION
Humans are constantly exposed to a background level of nuclear
radiation, from both natural and manmade sources. At most petroleum
drilling and production facilities, there is no incremental radiation
exposure from associated activities. At a few areas, however, naturally
occurring radioactive materials (NORM) can accumulate to levels
where a significant incremental exposure above background is possible,
3.8,1
Radioactive Decay
Radioactive decay occurs when the nucleus of an atom is in an
unstable energy state. It is the process used by the nucleus to reach a
more stable energy state. The three major types of radioactive decay
are alpha, beta, and gamma decay. Other types of decay, such as
spontaneous fission and spontaneous neutron emission, are possible but
occur very infrequently. Induced neutron emission and induced fission
can also occur when the nucleus has absorbed another particle, such
as an alpha particle or a neutron.
Alpha decay is the emission of a helium nucleus (doubly ionized
helium atom) from the nucleus of an unstable atom. Beta decay is the
ransformation of a neutron in the nucleus into a proton and an
electron. The proton remains in the nucleus and the electron is emitted.
In some cases of beta decay, a proton is transformed into a neutron
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and a positron (antielectron). The neutron remains in the nucleus and
the positron is emitted. Gamma decay is the lowering of the energy
of a nucleus through the emission of a photon of electromagnetic
radiation. In most cases, gamma decay is of most concern in the
petroleum industry.
Radioactive decay is the spontaneous change of a nucleus of an
atom. Because it is a random process, there is no way to predict when
a particular nucleus will decay. The decay of large numbers of atoms
can be modeled through a decay probability, however. When a large
number of nuclei are considered, the number of radioactive decay
events is proportional to the number of nuclei present,
_
dN
dt
=
,XT/ ,
XN(t)
(36)
where \ is a constant of proportionality that depends on the type of
nucleus and is a measure of the probability of decay for the nucleus.
N is the number of nuclei present. If multiple decay modes are
possible for a given nucleus, X is the sum of the decay probabilities
of each decay mode.
This equation can be solved for the number of nuclei as a function
of time:
N(t) = N(0)eXt
(37)
The most common measure of the rate of decay of radioactive
nuclei is the time for half of the nuclei to decay. This time is called
the half-life and can be expressed as
1
N(0)
2
XT
XT
(38)
where T is the halflife. The decay probability can be expressed in
terms of the halflife, yielding the following equation for the number
of nuclei as a function of time:
(39)
The Impact of Drilling and Production Operations
123
The decay rate of a group of radioactive nuclei can also be expressed
in terms of the total number of decay events per second, which is
called activity. Activity is the primary measure of the radioactivity of
a material. The units of activity are the Becquerel (Bq), which is equal
to 1 decay/sec. A more common unit of activity is the Curie, which
is equal to 3.7 x 1010 decays/sec.
A related measure of activity is the specific activity. For the specific
activity, the concentration of radioactive nuclei is typically normalized
in terms of activity per unit mass (for solids), activity per unit volume
(for fluids), or activity per unit area (for surfaces).
3.8.2 Health Physics
The study of the effects of nuclear radiation on human health is
the science of health physics. The effects of radiation are measured
in terms of exposure or dose. Exposure is defined as the electrical
charge released from ionization per unit mass of air. Dose is defined
as the energy from the radiation absorbed per unit mass of material.
One of the most widely used measures of radiation dose is the radia
tion absorbed dose (RAD), where
1 RAD = 100 erg/gram
The unit of RAD is not particularly useful for measuring human
exposure because it neglects the biological effects of radiation. Dif
ferent types of radiation have different biological effects for the same
energy deposition. To account for these different biological effects, the
RAD is multiplied by an empirical quality factor. The resulting value
is called the dose equivalent and its most common unit is the REM
(roentgen equivalent man). The quality factor for gamma radiation is
1 (one). Virtually all environmental impacts of nuclear radiation from
the petroleum industry are from gamma radiation.
The impact of radiation exposure also depends on the type of
radiation and where the source is located. The dose from alpha par
ticles from a source external to the body is zero, because alpha
particles cannot penetrate the skin and reach living cells. Beta particles
are able to penetrate the surface layers of the skin and can provide a
dose to living skin tissue. Any other exposure from alpha or beta
particles can come only from ingesting or inhaling the radionuclide
hat emits the particle. Gamma rays, on the other hand, can penetrate
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through a body. Thus, the dose from gamma rays is a whole body
dose, and all organs can be exposed. The dose from neutrons is very
complex and will not be discussed.
There are two major types of biological effects of radiation: those
affecting cells as a whole and those affecting the reproductive capacity
of the cells.
The major effect on cells as a whole is for the radiation to break
chemical bonds within the cell and create free radicals. The most
common free radicals are those created from the decomposition of
water, hydrogen and hydroxyl:
H2O > H+ + OH
Hydroxyls can combine to form hydrogen peroxide:
OH + OH » H2O2
Hydrogen peroxide is highly reactive and can react with most other
molecules in the cell, disrupting the cellular chemistry.
The most important genetic changes involve cellular reproduction.
If radiation breaks or alters the DNA molecules within a cell, the
ability of the cell to replicate itself is impaired. In most cases, any
alteration in the DNA prevents it from reproducing. In some cases,
however, the cell is able to reproduce, but the subsequent cells may
be mutated. Similar mutations in cells also arise from the elevated
temperatures of cooking, from drugs, and from exposure to chemicals.
Experience has shown that a onetime whole body dose of less than
about 50 REM will not result in any noticeable or measurable acute
effects. A dose an order of magnitude higher, e.g., 400500 REM, is
a lethal dose for 50% of those receiving it. Thus, the LD50 for humans
is about 500 REM, with death usually occurring about two months
after exposure. A dose above 1,000 REM is considered lethal for all
exposed, i.e., LD100 is about 1,000 REM.
Longterm effects from a single large exposure or from a chronic
lowlevel exposure may include loss of hair, eye cataracts, cancer, or
leukemia. Unfortunately, those effects also arise from causes other than
nuclear radiation so it is difficult to determine whether or not they
come from radiation exposure. In many cases, no effects will be
observed following exposure to radiation.
The Impact of Drilling and Production Operations
125
Natural and manmade sources of nuclear radiation provide an
average exposure of about 750 mREM/year per person. The natural
background exposure of nuclear radiation varies widely but averages
about 500 mREM/year. This exposure comes from cosmic rays, natur
ally occurring radioactive elements in the ground, the air (radon and
carbon14), and from naturallyoccurring elements in our bodies and
the foods we eat. Exposure from manmade radiation sources averages
about 250 mREM/year. Manmade sources include medical and dental
Xrays, smoking, color television, and luminous wristwatches. Nuclear
power plants contribute less than 1 mREM/year. Actual exposure levels
for any particular individual vary significantly.
The risks from nuclear radiation can also be placed in perspective
by comparing the estimated loss of life expectancy to that from other
health risks. As seen in Table 324, there is a finite risk, but it is small
compared to many other risks.
The International Commission on Radiological Protection has set
recommended exposure limits for radiation. The maximum recom
mended cumulative exposure to radiation is 5 REM per year. This level
Table 3-24
Estimated Loss of Life Expectancy from Health Risks
Health Risk
Loss of Life
Expectancy (days)
Smoking 20 cigarettes/day
Overweight by 20%
All accidents combined
Auto accidents
Alcohol consumption
Home accidents
Drowning
Safest jobs (teaching)
Natural background radiation
Medical xrays (U.S. average)
Natural catastrophes
1 rem occupational radiation dose
1 rem/year for 30 years
5 rem/year for 30 years
2,370 (6.5 years)
985 (2.7 years)
435 (1.2 years)
200
130
95
41
30
8
6
3.5
1
30
150
Source: Von Flatern, 1993.
Copyright Petroleum Engineer International, with permission.
126
Environmental Control in Petroleum Engineering
is one tenth the level that causes medically observable changes in
cellular chemistry. The maximum permitted occupational exposure is
one tenth of the maximum recommended exposure level (500 mREM/
yr), while the maximum permitted exposure to the general public is
one tenth of the occupational level (50 mREM/yr). These limits do
not include exposure from natural radiation or medical Xrays.
Radiation exposure limits are governed by the as low as reasonably
achievable (ALARA) concept. Under ALARA, all exposures are kept
to a minimum, even if the exposures are well below the maximum
recommended levels.
3.8.3
Naturally Occurring Radioactive Materials
In most cases, the level of NORM found at a site and the subse
quent dose from exposure are too low to represent a serious hazard
to employees. At a few sites, however, the potential exists for expo
sures that exceed the recommended levels after only a few hours. The
largest risk of NORM exposure is probably ingestion or inhalation of
NORM by workers handling and cleaning contaminated equipment.
Care must be taken to prevent buildup of NORMcontaminated scale
on the ground after cleaning out equipment. Because of its long half
life (1,622 years), Ra226 contaminated pipe yards could pose a health
threat to future development of the area, particularly in urban areas.
To determine the level of NORM at a site, radioactive assays are
conducted. The concentration of NORM in equipment or scale is
important in determining whether the material is considered radioactive
or not and how it can be disposed. These assays are expensive ($50
$150 per sample) and can take up to 90 days before the results become
available (Miller et al., 1990).
Because of the cost and time required to assay NORM levels to
determine handling and disposal options, several attempts have been
made to develop a relationship between the specific activity of NORM
to the levels of radiation around the equipment as measured by a hand
held detector (Carroll et al., 1990; Miller et al., 1990; Smith, 1987),
Additional work in the area is needed, however.
3.9 AIR POLLUTION
The primary impacts of air pollutant from production activities
comes from chronic exposure. For materials, the impact includes
The Impact of Drilling and Production Operations
127
soiling or chemical deterioration of surfaces. For plants, the impact
includes damage to chlorophyl and a disruption of photosynthesis. Sulfur
dioxide can also accumulate in soils, lowering the pH and modifying the
soil nutrient balance. The impact of air pollutants on humans and animals
includes irritation and damage to respiratory systems.
The impact of sulfur dioxide and hydrocarbons (ethene) has been
observed on plants at concentrations as low as 0.03 ppm and 0.05 ppm,
respectively. Sulfur dioxide concentrations on the order of 1 ppm can
cause constriction of airways in the respiratory tracts of humans
(Seinfeld, 1986).
3.10
ACOUSTIC IMPACTS
Some of the operations associated with drilling and production
can generate high noise (acoustic) levels. The impact of these
noises, however, is normally small. The most important sources are
the seismic operations used during exploration. A number of studies
have been conducted on ways to minimize the environmental impact
of these operations (Ruiz Soza, 1991; Wren, 1991; Wright, 1991;
Bertherin, 1991).
An extensive review of the acoustic impact of drilling and produc
tion on marine mammals was conducted by the American Petroleum
Institute (1989a). This review concluded that acoustic impacts from
offshore petroleum operations, including sounds from ships, aircraft,
seismic exploration, drilling, dredging, and production, are limited
primarily to shortterm responses by mammals. For example, an
airplane flyby can cause pinnipeds (seals and walruses) to jump into
the water, abandoning their young. No longterm impacts on marine
mammal populations have been observed, however. Explosives can
injure mammals in water within a few hundred meters, but seismic
air guns are not believed to be physically harmful unless the animals
are very close to the guns.
The effects of air guns on fish with swim bladders, e.g., anchovies,
was also studied (American Petroleum Institute, 1987b). The overall
effects of seismic surveys using air guns appears very small. Notice
able effects on eggs and larvae would only result from large numbers
of multiple exposures to full seismic arrays. The largest reduction in
survival rate (35%) was for fourdayold larvae exposed 34 times to
air guns passing overhead at a distance of 10 feet. Seismic pulses with
air guns appear to have a lethal radius for fish of about 1-2 meters.
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Environmental Control in Petroleum Engineering
The effect of chronic noise from underwater drilling on the behavioral
and physiological responses of belukha whales has also been studied
(American Petroleum Institute, 1986b). It was found that belukha
whales, like other toothed cetaceans, have a hearing range of greatest
sensitivity different from the frequency range of most industrial
sounds. The only response to the sound observed was a startle res
ponse at the start of each playback session in a pool containing four
whales. Thus, little effect on whale health or behavior is expected from
drilling activities.
3.11
EFFECTS OF OFFSHORE PLATFORMS
When properly managed, the actual environmental impact of offshore
exploration and production activities is very low. In some cases, the
presence of offshore platforms can be beneficial. The subsea structure
(jacket) provides a substrate for marine flora to grow. This growth is
particularly important in areas where few rocks are found on the bottom
to provide such a substrate, e.g., in the Gulf of Mexico or other deltaic
systems. This flora then attracts fauna of different types and sizes.
Eventually large fish are attracted to the platform, yielding a much higher
fish concentration than is found in the open ocean. This high fish concen
tration provides enhanced commercial and recreational fishing opportunities,
When an offshore field is abandoned, the platform must be removed.
The least expensive and safest method for platform removal has been to
use explosives to sever the piles and conductor pipes below the mudline.
The use of underwater explosives for this purpose, however, can be lethal
to aquatic life swimming nearby. Monitoring of the surrounding area
(within 1,000 yards) is now required in some areas before the charges
can be detonated. Any endangered species in the area, such as sea turtles,
must be removed before detonation. Other methods to sever the platform
from its anchorage that have been considered include acid cutting,
embrittlement through liquid nitrogen freezing, solid fuel cutting torches,
water blasting, and mechanical cutters. These methods, however, may
result in greater safety hazards to the personnel implementing them.
3.12
RISK ASSESSMENT
Risk assessment provides a numerical estimate of the probability of
potentially adverse health effects from human exposure to environmental
The Impact of Drilling and Production Operations
129
hazards. It identifies what the potential hazards may be, their potential
impact, how many humans could be impacted, and what the overall
impact might be.
Risk assessment can be used to identify and rank the substances
that have the greatest potential environmental impact. This helps
companies identify and prioritize efforts to ensure environmentally safe
operations. Risk assessment studies also document environmentally
responsible actions and can be used as a scientifically defensible study
if litigation occurs. Risk assessment studies are expensive, however,
and may not be feasible for small operations. They are normally
required only for new emission sources or modified stationary sources.
The calculations are complex and based on various exposure pathways.
Sullivan (1991) provides a discussion of risk assessment for crude oil
contamination.
Risk assessment consists of four steps: hazard identification, dose
response assessment, exposure assessment, and risk characterization.
Hazard Identification determines the nature and amount of toxic
pollutants that could potentially be emitted. It identifies the potential
adverse health effects associated with those pollutants. Hazard identifi
cation includes a qualitative review of the available information of
each substance to determine which substances should be included in
a detailed assessment. It also determines the potential exposure path
ways for the spread of the pollutant following a release e.g., ground
water or airborne transport, and the affected populations. Information
for hazard identification can be obtained from relevant federal, state,
and local regulations, risk assessment studies from similar facilities,
Material Safety Data Sheets, and technical journals.
Dose-Response Assessment determines the relationship between the
magnitude of an exposure to a substance and the occurrence of specific
health effects. It involves determining the actual toxicity of each
substance identified in the hazard identification. Doseresponse assess
ment includes obtaining a description of the toxic properties of the
substances, including acute (short term) effects, noncarcinogenic
chronic (longterm) effects, and the carcinogenic potential for different
dose levels. The result of this assessment is a probability estimate of
the incidence of the adverse effect as a function of human exposure
level to the substance.
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Environmental Control in Petroleum Engineering
The hazards of noncarcinogenic substances are evaluated relative
to an allowable daily exposure level called the reference dose. The
reference dose is the maximum daily dose of a substance to which a
human may be exposed and not be adversely affected. In most cases,
this dose is based on nontoxic exposure levels in animals that are
extrapolated to humans with safety factors. This method assumes that
exposures have a threshold below which no adverse effects will occur.
Carcinogenic substances are evaluated using a model for the prob
ability of a human developing cancer. Either animal or human data
(when available) are used in developing the probabilities. These
substances are normally assumed to have no threshold levels, and all
effects are extrapolated to zero exposure levels. Regulatory agencies
establish quantitative limits for exposure that are based on the pro
jected "excess cancer risk" caused by exposure to individual sources.
Cancer risk is typically estimated for a lifetime exposure (70 years)
and is expressed as a probability of developing cancer within a lifetime
as in the term "one chance in one million." The U.S. Environmental
Protection Agency has developed doseresponse relationships for many
compounds, but their values should be critically reviewed before being
used because they change as new data become available.
Exposure Assessment determines the extent of potential human exposure
to any emitted substances. Its goal is to accurately estimate both the
dose that reaches the person (the administered dose) and the dose that
reaches the target tissue within the body (the target dose). It quantifies
all potential transport routes for each substance, e.g., groundwater or
airborne transport, and considers three types of exposure—ingestion,
inhalation, and dermal (skin) adsorption. Human exposures are reported
as maximum daily doses for noncarcinogens and lifetime average daily
doses for carcinogens.
Exposure assessment includes characterizing the emissions, model
ing dispersion of the emissions, and quantifying the resulting exposures
from each pathway. It estimates the probable magnitude, duration,
timing, and route of exposure and the size and nature of the population
exposed, and provides uncertainties for these estimates.
A critical part of exposure assessment includes working with the
relevant regulatory agencies to ensure that the proper type of tests and
measurements are conducted. Unfortunately, there are few standard expo
sure evaluation methods for most substances. The U.S. Environmental
The Impact of Drilling and Production Operations
131
Protection Agency has developed a set of air quality models that can
be used for airborne pollutant transport,
Risk Characterization describes the nature, magnitude, and uncertainty
of the health risks associated with each pollutant. It is the combination
of the doseresponse assessment and the exposure assessment. Risk
characterization determines a quantitative estimate for the risk. This
risk level can then be compared to a risk level that is considered to
be insignificant. In humans, risk levels of one in ten thousand and one
in one million are often used by regulatory agencies as benchmarks
for acceptable risk levels.
The risk to the "maximumexposed individual," i.e., the individual
who receives the worstcase exposure scenario, and the more realistic
risk to the general population should both be determined. Risk charac
terization should include a discussion of background levels of pollu
tants and risks associated with other activities, including the risks if
nothing is done. Finally, risk characterization should be flexible and
incorporate an honest evaluation of the uncertainties of the information
used in the analysis.
Acceptable risk for carcinogens is normally determined in one of
two ways. The most common approach is to calculate the maximum
risk for an individual assuming an exposure level at the highest
predicted longterm concentration. The goal of this approach is to limit
excess lifetime cancer risks to a predetermined level. The second
method is to estimate the aggregate incidence of potential excess
cancer cases for the exposed population within the vicinity of the
source. Risk assessment studies have uncertainties, particularly when
conservative data are used. If more realistic data are used with Monte
Carlo simulation, a more realistic estimate of risk can be obtained
(Gordon and Cayias, 1993).
American Petroleum Institute, "Fate and Effects of Polynuclear Aromatic
Hydrocarbons in the Aquatic Environment," API Publication 4297,
Washington, D.C., May 1978.
American Petroleum Institute, "Analysis of Mussel (Mytilus californianus)
Communities in Areas Chronically Exposed to Natural Oil Seepage," API
Publication 4319, Washington, D.C., May 1980.
132
Environmental Control in Petroleum Engineering
American Petroleum Institute, "Fate and Effects of Experimental Oil Spills
in an Eastern Coastal Marsh System," API Publication 4342, Washington,
D.C., Sept. 1981a.
American Petroleum Institute, "The Sources, Chemistry, Fate, and Effects of
Chromium in Aquatic Environments," Washington, D.C., Nov. 1981b.
American Petroleum Institute, "Summary and Analysis of API Onshore
Drilling Mud and Produced Water Environmental Studies," API Bulletin
D19, Washington, D.C., Nov. 1983.
American Petroleum Institute, "Effects of Petroleum Residues on Inter
tidal Organisms of Bermuda," API Publication 4355, Washington, D.C.,
1984a.
American Petroleum Institute, "Fish and Offshore Oil Development," API
Publication 87559302, Washington, D.C., 1984b.
American Petroleum Institute, "Toxicity of Dispersed and Undispersed
Prudhoe Bay Crude Oil Fractions to Shrimp, Fish, and Their Larvae," API
Publication 4441, Washington, D.C., Aug. 1985a.
American Petroleum Institute, "Oil Effects on Spawning Behavior and
Reproduction in Pacific Herring (Clupea harengus pallasi)" API Publi
cation 4412, Washington, D.C., Oct. 1985b.
American Petroleum Institute, "Methods of Storage, Transportation, and
Handling of Drilling Fluid Samples," API Publication 4399, Washington,
D.C., March, 1985c.
American Petroleum Institute, "Chronic Effects of Drilling Fluids Discharged
to the Marine Environment," API Publication 4397, Washington, D.C., June
!985d.
American Petroleum Institute, "Influence of Crude Oil and Dispersant on the
Ability of Coho Salmon to Differentiate Home Water from NonHome
Water," API Publication 4446, Washington, D.C., Dec. 1986a.
American Petroleum Institute, "Underwater Drilling—Measurement of Sound
Levels and Their Effects on Belukha Whales," API Publication 4438,
Washington, D.C., March 1986b.
American Petroleum Institute, "Effects of Crude Oil and Chemically Dis
persed Oil on Chemoreception and Homing in Pacific Salmon," API
Publication 4445, Washington, D.C., June 1987a.
American Petroleum Institute, "Effects of Airgun Energy Releases on the
Northern Anchovy," API Publication 4453, Washington, D.C., Dec. 1987b.
American Petroleum Institute, "Field Studies on the Reproductive Effects of
Oil and Emulsion on Marine Birds," API Publication 4466, Washington,
D.C., Oct. 1988.
American Petroleum Institute, "Effects of Offshore Petroleum Operations on
Cold Water Marine Mammals: A Literature Review," API Publication 4485,
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The Impact of Drilling and Production Operations
133
American Petroleum Institute, "API Environmental Guidance Document;
Onshore Solid Waste Management in Exploration and Production Opera
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American Petroleum Institute, "Fate and Effects of Drilling Fluid and Cut
ting Discharges in Shallow, Nearshore Waters," API Publication 4480,
Washington, D.C., Sept. 1989c.
American Petroleum Institute, "Fate and Effects of Produced Water Dis
charges in Nearshore Marine Waters," API Publication 4472, Washington,
D.C., Jan. 1989d.
American Petroleum Institute, "Bioaccumulation of Polycyclic Aromatic
Hydrocarbons and Metals in Estuarine Organisms," API Publication 4473,
Washington, D.C., May 1989e.
American Petroleum Institute, "Rapid Bioassay Procedures for Drilling
Fluids," API Publication 4481, Washington, D.C., March 1989f.
Arscott, R. L., "'New Directions in Environmental Protection in Oil and Gas
Operations," /. Pet. Tech., April 1989, pp. 336342.
Ayers, R. C, Jr., Sauer, T. C., Jr., and Anderson, P. W., "The Generic Mud
Concept for NPDES Permitting of Offshore Drilling Discharges," J, Pet.
Tech., March 1985, pp. 475–478.
Baker, K. A., "The Effect of the Lodgepole Sour Gas Well Blowout on
Coniferous Tree Growth: Damage and Recovery," paper SPE 23331 pre
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on Health, Safety, and Environment, The Hague, Netherlands, Nov. 1014,
1991.
Bakke, T., Gray, J. S., and Reiersen, L. O., "Monitoring in the Vicinity of
Oil and Gas Platforms: Environmental Status in the Norwegian Sector in
19871989," Proceedings of the U.S. Environmental Protectional Agency's
First International Symposium on Oil and Gas Exploration and Produc
tion Waste Management Practices, New Orleans, LA, Sept. 1013, 1990,
pp. 623634.
Bertherin, G., "Seismic Techniques in Guatemala: An Approach Yielding a
New Dimension to Environmental Protection," paper SPE 23520 presented
at the Society of Petroleum Engineers First International Conference on
Health, Safety, and Environment, The Hague, Netherlands, Nov. 1014,
1991.
Bozzo, W., Chatelain, M., Salinas, J., and Wiatt, W., "Brine Impacts to a
Texas Salt Marsh and Subsequent Recovery," Proceedings of the U.S.
Environmental Protection Agency's First International Symposium on Oil
and Gas Exploration and Production Waste Management Practices, New
Orleans, LA, Sept. 1013, 1990, pp. 129140.
Branch, R, T., Artiola, J., and Crawley, W. W., "Determination of Soil
Conditions that Adversely Affect the Solubility of Barium in Nonhazardous
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Oilfield Waste," Proceedings of the U.S. Environmental Protection Agency's
First International Symposium on Oil and Gas Exploration and Produc
tion Waste Management Practices, New Orleans, LA, Sept. 10–13, 1990,
pp. 217226.
Burnham, K. and Bey, M., "Effects of Crude Oil and Ultraviolet Radiation
on Immunity Within Mouse Skin," ./. Toxicology and Environmental
Health, Vol. 34, 1991, pp. 8393.
Burnham, K. and Rahman, M., "Effects of Petrochemicals and Ultraviolet
Radiation on Epidermal IA Expression In Vitro," J. Toxicology and Environmental Health, Vol. 35, 1992, pp. 175185.
Calabrese, E. J. and Kenyon, E. M., Air Toxics and Risk Assessment. Chelsea,
Michigan: Lewis Publishers, Inc., 1991.
Candler, J., Leuterman, A., Wong, S., and Stephens, M., "Sources of Mercury
and Cadmium in Offshore Drilling Discharges," paper SPE 20462 pre
sented at the Society of Petroleum Engineers 65th Annual Technical
Conference and Exhibition, New Orleans, LA, Sept. 2325, 1990.
Carrol], J. F., Gunn, R. A., and O'Brien, M. S., "Naturally Occurring
Radioactive Material Logging," paper SPE 20616 presented at the Society
of Petroleum Engineers 65th Annual Technical Conference and Exhibition,
New Orleans, LA, Sept. 2325, 1990.
Conklin, P. J. and Rao, K. R., "Comparative Toxicity of Offshore and Oil
Added Drilling Muds to Larvae of Palaemonetes intermedius," Archives of
Environmental Contamination and Toxicology, Vol. 13, 1984, pp. 685690.
Crawley, W. W. and Branch, R. T., "Characterization of Treatment Zone Soil
Conditions at a Commercial Nonhazardous Oilfield Waste Land Treatment
Unit," Proceedings of the U.S. Environmental Protection Agency's First
International Symposium on Oil and Gas Exploration and Production Waste
Management Practices, New Orleans, LA, Sept. 1013, 1990, pp. 147158.
De Jong, S. A., Zevenboom, W., Van Het Groenewoud, H., and Daan, R.,
"Short and LongTerm Effects of Discharged OBM Cuttings, With and
Without Previous Washing, Tested in Field and Laboratory Studies on the
Dutch Continental Shelf, 19851990," paper SPE 23353 presented at the
Society of Petroleum Engineers First International Conference on Health,
Safety, and Environment," The Hague, Netherlands, Nov. 1014, 199la.
De Jong, S. A., Marquenie, J. M., Van't Zet, J., and Zevenboom, W., "Pre
liminary Results on DoseEffect Relationships of Thermally Treated Oil
Containing Drilled Cuttings in Boxcosms," paper SPE 23355 presented at
the Society of Petroleum Engineers First International Conference on Health,
Safety, and Environment," The Hague, Netherlands, Nov. 10–14, 199Jb.
Derkics, D. L. and Souders, S. H., "Pollution Prevention and Waste Mini
mization Opportunities for Exploration and Production Operations," paper
SPE 25934 presented at the Society of Petroleum Engineers/Environmental
The Impact of Drilling and Production Operations
135
Protection Agency's Exploration and Production Environmental Conference,
San Antonio, TX, March 7–10, 1993.
Deuel, L. E., "Evaluation of Limiting Constituents Suggested for Land
Disposal of Exploration and Production Wastes," Proceedings of the U.S.
Environmental Protection Agency's First International Symposium on
Oil and Gas Exploration and Production Waste Management Practices,
Sept, 10–13, New Orleans, LA, 1990, pp. 411430.
Gordon, R. D. and Cayias, J. L., "An Approach to Resolve Uncertainty in
Quantitative Risk Assessment," paper SPE 25959 presented at the Society
of Petroleum Engineers/Environmental Protection Agency's Exploration and
Production Environmental Conference, San Antonio, TX, March 7–10.
1993.
Hastings, L., Cooper, G. P., and Burg, W., "Human Sensory Response to
Selected Petroleum Hydrocarbons," in Applied Toxicology of Petroleum
Hydrocarbons, H. N. McFarland et al. (editors). Princeton: Princeton
Scientific Publishers, 1984, pp. 255270
Hoskin, S. J. and Strohl, A. W., "OnSite Monitoring of Drilling Fluid
Toxicity," paper SPE 26005 presented at the Society of Petroleum Engineers/
Environmental Protection Agency's Exploration and Production Environ
mental Conference, San Antonio, TX, March 710, 1993.
Hudgins, C. M., Jr., "Chemical Treatments and Usage in Offshore Oil and
Gas Production Systems," J. Pet. Tech., May 1992, pp. 604611.
Jones, F. V., Rushing, J. H., and Churan, M. A., "The Chronic Toxicity of
Mineral Oil—Wet and Synthetic Liquid—Wet Cuttings on an Estuarine
Fish, Fundulus grandis," paper SPE 23497 presented at the Society of
Petroleum Engineers First International Conference on Health, Safety, and
Environment, The Hague, Netherlands, Nov. 1014, 1991,
Kaszuba, J. P. and Buys, M W,, "Reclamation Procedures for Produced Water
Spills from Coalbed Methane Wells, San Juan Basin, Colorado and New
Mexico," paper SPE 25970 presented at the Society of Petroleum Engineers/
Environmental Protection Agency's Exploration and Production Environ
mental Conference, San Antonio, TX, March 710, 1993.
Logan, T. H. and Traina, S. J., "Trace Metals in Agricultural Soils," in Metals
in Groundwater, H. E. Allen, E. M. Perdue, and D. S. Brown, (editors).
Chelsea, Michigan: Lewis Publishers, Inc., 1993, an imprint of CRC Press,
Boca Raton, FL, pp. 311312.
MacFarlane, K. and Nguyen, V. T., "The Deposition of Drill Cuttings on the
Seabed," paper SPE 23372 presented at the Society of Petroleum Engineers
First International Conference on Health, Safety, and Environment, The
Hague, Netherlands, Nov. 1014, 1991.
Macyk, T. M., Nikiforuk, F. L, and Weiss, D. K., "Drilling Waste Land
spreading Field Trial in the Cold Lake Heavy Oil Region, Alberta, Canada,"
136
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Proceedings of the U.S. Environmental Protection Agency's First Inter
national Symposium on Oil and Gas Exploration and Production Waste
Management Practices, New Orleans, LA, Sept. 1013, 1990, pp. 267280.
Maddin, C. M,, "Marine Toxicity and Persistence of Surfactants Used in the
Petroleum Producing Industry," paper SPE 23354 presented at the Society
of Petroleum Engineers First International Conference on Health, Safety,
and Environment, The Hague, Netherlands, Nov. 1014, 1991,
Mancini, E. R. and Stilwell, C. T., "Biotoxicity Characterization of a Produced
Water Discharge in Wyoming," J. Pet, Tech., June 1992, pp. 744–748.
Miller, R. W., "Effects of Drilling Fluids Components and Mixtures on Plants
and Soils," API Project Summary: 19741977, 1978, p. 33.
Miller, H. T., Bruce, E. D., and Scott, L. M., "A Rapid Method for the
Determination of the Radium Content of Petroleum Production Wastes,"
Proceedings of the U.S. Environmental Protection Agency's First Inter
national Symposium on Oil and Gas Exploration and Production Waste
Management Practices, Sept. 1013, New Orleans, LA, 1990, pp. 809820.
Mosley, H. R., "Summary of API Onshore Drilling Mud and Produced Water
Environmental Studies," paper SPE 11398 presented at the Society of
Petroleum Engineers 1983 IADC/SPE Drilling Conference, New Orleans,
LA, Feb. 2023.
Mount, D. R., Gulley, D. D., and Evans, J. M., "Saiinity/Toxicity Relation
ships to Predict the Acute Toxicity of Produced Waters to Freshwater
Organisms," paper SPE 26007 presented at the Society of Petroleum
Engineers/Environmental Protection Agency's Exploration and Production
Environmental Conference, San Antonio, TX, March 7—10, 1993.
National Research Council, Oil in the Sea: Inputs, Fates, and Effects,
Washington, D.C.: National Academy Press, 1985.
Offshore, "Drilling Fluid Product Directory: Part I," Sept. 1991 a, p. 43.
Offshore, "Drilling Fluid Product Directory: Part II," Oct. 1991b, p. 62.
Parrish, P. R. and Duke, T. W., "Variability of the Acute Toxicity of Drilling
Fluids to Mysids (Mysidopsis bahia)" American Society for Testing and
Materials, Special Technical Publication 976, 1988.
Parrish, P. R. and Duke, T. W., "Effects of Drilling Fluids on Marine
Organisms," in Ocean Processes in Marine Pollution, Vol. 6, Physical and
Chemical Processes: Transport and Transportation, D. J. Baumgartner and
I. W. Duedall (editors). Malabar, Florida: Krieger Publishing Co., 1990.
Parrish, P. R., Macauley, J. M., and Montgomery, R. M., "Acute Toxicity of
Two Generic Drilling Fluids and Six Additives, Alone and Combined, to
Mysids (Mysidopsis bahia)" in Drilling Wastes, F. R. Engelhard, J. P. Ray,
and A. H. Gillam (editors). New York: Elsevier, 1989, pp. 415426.
Peresich, R. L., Burrell, B. R., and Prentice, G. M. "Development and Field
Trial of a Biodegradable Invert Emulsion Fluid," paper SPE/IADC 21935
The Impact of Drilling and Production Operations
137
presented at the 1991 Drilling Conference, Amsterdam, The Netherlands,
March 11–14, 1991.
Proctor, N. H., Hughes, J. P., and Fischman, M. L., Chemical Hazards of
the Workplace, New York: Van Nostrand Reinhold, 1989.
Rabalais, N. N., Means, J., and Boesch, D., "Fate and Effects of Produced
Water Discharges in Coastal Environments," Proceedings of the U.S.
Environmental Protection Agency's First International Symposium on Oil
and Gas Exploration and Production Waste Management Practices, New
Orleans, LA, Sept. 10–13, 1990, pp. 503–514.
Ruiz Soza, O., "Maturin East Seismic Program: Environmental Impact
Assessment," paper SPE 23388 presented at the Society of Petroleum
Engineers First International Conference on Health, Safety, and Environ
ment, The Hague, Netherlands, Nov. 10–14, 1991.
Rushing, J. H., Churan, M. A., and Jones, F. V., "Bioaccumulation From
Mineral Oil—Wet and Synthetic Liquid—Wet Cuttings in an Estuarine
Fish, Fundulus grandis," paper SPE 23350 presented at the Society of
Petroleum Engineers First International Conference on Health, Safety, and
Environment, The Hague, Netherlands, Nov. 1014, 1991.
RyerPower, J. E., Custance, S. R., and Sullivan, M. J., "Determination of
Reference Doses for Mineral Spirits, Crude Oil, Diesel Fuel No. 2, and
Lubricating Oil," paper SPE 26398 presented at the Society of Petroleum
Engineers 68th Annual Technical Conference and Exhibition, Houston, TX,
Oct. 3–6, 1993.
Seinfeld, J. H., Atmospheric Chemistry and Physics of Air Pollution, New
York: John Wiley and Sons, 1986.
Smith, A. L., "RadioactiveScale Formation," J. Pet. Tech., June 1987,
pp. 697706.
St. Pe, K. M., Means, J., Milan, C, Schlenker, M., and Courtney, S., "An
Assessment of Produced Water Impacts to LowEnergy, Brackish Water
Systems in Southeast Louisiana: A Project Summary," Proceedings of the
U.S. Environmental Protection Agency's First International Symposium on
Oil and Gas Exploration and Production Waste Management Practices, New
Orleans, LA, Sept. 10–13, 1990, pp. 31–42.
Sullivan, M. J., "Evaluation of Environmental and Human Risk from Crude
Oil Contamination," J. Pet. Tech., Jan. 1991, pp. 14–16.
Tchobanoglous, G. and Burton, F. L., Wastewater Engineering: Treatment,
Disposal, and Reuse. New York: McGraw Hill., Inc, 1991.
U.S. Bureau of Land Management, "Ecological Investigations of Petroleum
Production Platforms in the Central Gulf of Mexico," BLMYMYMP/T
814)183331, NTIS No. PB82167834, 1981.
U.S. Environmental Protection Agency, "Effects of Drilling Fluids on Embryo
Development," EPA 600/383021, Washington, D.C., 1983.
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U.S. Environmental Protection Agency, "Acute and Chronic Toxicity
of Produced Water to Mysids (Mysidopsis bahia)" EPA/600/X89/175,
Washington, D.C., April 1989.
U.S. Salinity Staff, "Diagnosis and Improvement of Saline and Alkali Soils,"
Agriculture Handbook 68, U.S. Department of Agriculture, 1954.
Valkovic, V., Trace Elements in Petroleum, Tulsa: Petroleum Publishing
Company, 1978.
Vickers, D. T., "Disposal Practices for Waste Waters from Coalbed Methane
Extraction in the Black Warrior Basin, Alabama," Proceedings of the U.S.
Environmental Protection Agency's First International Symposium on
Oil and Gas Exploration and Production Waste Management Practices,
Sept. 1013, New Orleans, LA, 1990, pp. 255266.
Von Flatern, R., "NORM Contamination Regulations Threaten Industry
Economy," Petroleum Engineer International, May 1993, pp. 3639.
Whale, G. F. and Whitham, T. S., "Methods for Assessing Pipeline Corrosion
Prevention Chemicals on the Basis of Antimicrobial Performance and Acute
Toxicity to Marine Organisms," paper SPE 23357 presented at the Society
of Petroleum Engineers First International Conference on Health, Safety,
and Environment, The Hague, Netherlands, Nov. 1014, 1991,
Wojtanowicz, A. K., "Environmental Control Potential of Drilling Engineer
ing: An Overview of Existing Technologies," paper SPE/IADC 21954
presented at the Society of Petroleum Engineers 1991 Drilling Conference,
Amsterdam, The Netherlands, March 1114, 1991.
Wojtanowicz, A. K., Shane, B. S., Greenlaw, P. N., and Stiffey, A. V.,
"Cumulative Bioluminescence—A Potential Rapid Test of Drilling Fluid
Toxicity: Development Study," SPE Drilling Engineering, March 1992,
pp. 3946.
Wren, J. M., "Minimizing the Environmental Impact of Seismic Operations
in Canada and Alaska," paper SPE 23386 presented at the Society of
Petroleum Engineers First International Conference on Health, Safety, and
Environment, The Hague, Netherlands, Nov. 1014, 1991.
Wright, N. H., "Optimal Environmental Strategies: Fit for Exploration," paper
SPE 23387 presented at the Society of Petroleum Engineers First Inter
national Conference on Health, Safety, and Environment, The Hague,
Netherlands, Nov. 1014, 1991.
CHAPTER 4
Environmental
Transport of
Petroleum Wastes
The environmental impact of most releases of petroleum industry
wastes would be minimal if the wastes remained at their points of
release. Unfortunately, wastes can migrate away from a release point
by a number of pathways. These pathways include transport along the
surface of the earth or along the surface of a body of water, transport
through the soil through the pore structure, and transport through the
air. These migration pathways are briefly discussed below.
4.1
SURFACE PATHS
Surface pathways of transport are those where the released material
travels along either the soil or open water surface. Surface transport
of petroleum wastes from releases on land occurs primarily when high
volumes of liquid wastes are discharged onto the ground or when
stormwater sweeps through a site. These liquids then flow down
topographical drainage features until they either mix with existing
surface waters, evaporate, or enter the pore network of the earth they
flow over. Dikes and diversion trenches can be used to control such
surface migration.
Surface transport of petroleum wastes on open water can occur
with hydrocarbons because they are lighter than water. This trans
port of hydrocarbons will be controlled by natural water currents and
wind. Because virtually all natural water currents are parallel to the
shoreline, the primary direction of transport will be parallel to the
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shoreline. If an onshore wind blows across the hydrocarbons, they
can be pushed to shorelines. Hydrocarbons spilled on water will
either evaporate, enter the water column, ground on the shore, or be
naturally degraded.
4.2
SUBSURFACE PATHS
Subsurface pathways of transport are those where released liquids
enter the pore structure of soil or sinks below the surface of open waters.
4.2.1
Releases on Land
There are two primary types of subsurface transport for onshore
releases that can impact the environment: the transport of fluids at or
above the water table from surface spills and the transport of fluids
from one geologic formation to another through improperly plugged
and abandoned wells.
When petroleum industry materials are discharged onto the ground,
the liquid fraction, including any dissolved chemicals, begins to enter
the pore network. These materials can travel through soil pore network
in four ways. First, a separate nonaqueous phase liquid (NAPL) can
flow through the pores. Second, contaminants can dissolve into ground
water and be transported by it. Third, very small solids (colloids) can
also be transported with the water, although large particles will be
filtered by the porous media. Fourth, volatile contaminants can be
transported as a vapor through the vadose (air saturated) zone.
The transport of wastes through groundwater depends on a number
of factors, including the permeability of the soil, capillary pressure
between phases 'in the soil, solubility of the waste, partitioning coeffi
cients, adsorption properties, and volatility. Adsorption, partitioning
and volatilization decrease the concentration of chemicals in water,
while leaching, desorption, and runoff increase the concentration. A
review of the mechanisms of hydrocarbon transport in groundwater
has been presented by Hunt et al. (1988a, 1988b).
Metals tend to form insoluble complexes in highpH environments,
minimizing their ability to leach away from a site (American Petrol
eum Institute, 1983b). The primary mechanisms for the fixation of
metals by soils are absorption, ion exchange, and chemical precipita
tion. Ion exchange and adsorption are surface phenomena that are
Environmental Transport of Petroleum Wastes
141
highly dependent on soil type and composition, particularly the amount
of clays present. Factors that affect adsorption are the structural
characteristics of the chemical, the organic content of the soil, the pH
of the fluid medium, the soil grain size, the ion exchange capacity of
the soil (clay content), and the temperature. Migration of heavy metals
away from drill sites generally does not occur.
A number of numerical models having different levels of capabilities
are available (American Petroleum Institute, 1986, and American
Petroleum Institute, 1988). Unfortunately, most models neglect capil
lary trapping of the oil and air and hysteresis of relative permeability.
Monte Carlo models allowing multiple realizations of possible con
taminant transport have also been developed (Parker et al., 1993),
Another important pathway for the transport of petroleum wastes
is improperly plugged and abandoned wells. These wells allow fluids
from geologic formations having high hydrocarbon, salt, and/or heavy
metals concentrations to flow into formations containing fresh water.
Wells that are properly plugged and abandoned do not provide a
permeable flow channel for fluids. Fluid flow, however, is not possible
between layers if they are in hydrostatic pressure equilibrium, regard
less of whether channels exist between the layers.
Numerical modeling of fluid flow in improperly abandoned wells
can indicate the likelihood of freshwater contamination at a particular
site (Warner and McConnell, 1993). The relative contamination poten
tial of abandoned wells ranges from highly likely to impossible,
depending on the age of the well, the depth of the well, the type of
well, how the well was constructed, how it was plugged, the history
of well activity, and the hydrogeologic conditions at the site,
4.2.2
Releases on Water
Transport of petroleum wastes below the surface of water depends
primarily on the currents in the water and the topography of the floor
of the water body. Produced waters typically have a greater salinity
than fresh water or seawater, making them more dense. Discharged
produced waters then sink until they either reach a density equilibrium
with the seawater or reach the sea floor. Numerical models have been
developed to model the transport of discharged drilling muds and
produced water (Arscott, 1989). Two such models are the EPA's
CORMIX1 and the Offshore Operators Committee models.
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4.3 ATMOSPHERIC PATHS
Many petroleum industry wastes are gaseous and will be dispersed
into the air, where they are transported with the wind. Upon release,
airborn pollutants undergo transport by wind (advection), dispersion
from atmospheric turbulence, and removal from deposition on the ground,
vegetation, and buildings. Chemical transformations may also take place
that alter the chemical and/or physical state of the emitted pollutant.
Onshore sources of air pollutants are generally regulated by the total
emission rates, while offshore sources are generally regulated so that
the resulting onshore levels of pollutants are below specified levels.
To obtain permits to emit air pollutants for many applications, air
quality modeling is required (Sheehan, 1991). Such modeling relates
the downwind concentration of released pollutants to their emission
rates. Computerbased models are available that use information on
the emission rate, physical characteristics of the emission source, the
topography of the terrain over which the pollutants travel, and the mete
orological conditions of the area to calculate the pollutant concentration
downwind of the source (Moroz, 1987; Smith, 1987; American Petrol
eum Institute, 1983a; American Petroleum Institute, 1984; American
Petroleum Institute, 1985a; American Petroleum Institute, 1985b). A
discussion of models accepted by the U.S. Environmental Protection
Agency is available (U.S. Environmental Protection Agency, 1986),
REFERENCES
American Petroleum Institute, "Model Performance Evaluation for Offshore
Releases," API Publication 4387, Washington, D.C., Dec. 1983a.
American Petroleum Institute, "Summary and Analysis of API Onshore
Drilling Mud and Produced Water Environmental Studies," API Bulletin
D19, Washington, D.C., Nov. 1983b.
American Petroleum Institute, "Dispersion of Emissions from Offshore Oil
Platforms—A WindTunnel Modeling Evaluation," API Publication 4402,
Washington, D.C., May 1984.
American Petroleum Institute, "Plume Rise Assessment Downwind of Oil
Platforms for Neutral Stratification," API Publication 4420, Washington,
D.C., Dec. 1985a.
American Petroleum Institute, "Development and Application of a Simple
Method for Evaluating Air Quality Models," API Publication 4409,
Washington, D.C., Jan. 1985b.
Environmental Transport of Petroleum Wastes
143
American Petroleum Institute, "Review of GroundWater Models," API
Publication 4434, Washington, D.C., 1986.
American Petroleum Institute, "Phase Separated Hydrocarbon Contaminant
Modeling for Corrective Action," API Publication 4474, Washington, D.C.,
Oct. 1988.
Arscott, R. L., "New Directions in Environmental Protection in Oil and Gas
Operations," /, Pet. Tech., April 1989, pp. 336342.
Hunt, J. R., Sitar, N., and Udell, K. S., "Nonaqueous Phase Liquid Transport
and Cleanup: 1. Analysis of Mechanisms," Water Resources Research, Vol.
24, No. 8, Aug. 1988a, pp. 12471258.
Hunt, J. R., Sitar, N., and Udell, K. S., "Nonaqueous Phase Liquid Transport
and Cleanup: 2. Experimental Studies," Water Resources Research, Vol.
24, No, 8, Aug. 1988b, pp. 12591269.
Moroz, W. J., "Air Pollution Concentration Prediction Models," in Air
Pollution, E. E. Pickett. New York: Hemisphere Publishing Company, 1987.
Parker, J. C., Kahrarnan U., and Kemblowski, M. W., "A Monte Carlo Model
to Assess Effects of LandDisposed E&P Waste on Groundwater," paper
SPE 26383 presented at the Society of Petroleum Engineers 68th Annual
Technical Conference and Exhibition, Houston, TX, Oct. 36, 1993.
Sheehan, P. E., "Air Quality Permitting of Onshore Oil and Gas Production
Facilities in Santa Barbara County, California," paper SPE 21767 presented
at the Society of Petroleum Engineers Western Regional Meeting, Long
Beach, CA, March 20–22, 1991.
Smith. B. P., "Exposure and Risk Assessment," in Hazardous Waste Management Engineering, E. J. Martin, and J, H. Johnson, Jr. (editors). New
York:Van Nostrand Reinhold Company, Inc., 1987.
U.S. Environmental Protection Agency, "Guidelines on Air Quality Models
(Revised)," EPA450/278R, Research Triangle Park, NC, 1986.
Warner, D. L. and McConnell, C. L., "Assessment of Environmental Impli
cations of Abandoned Oil and Gas Wells," J. Pet. Tech., Sept. 1993,
pp. 874–880.
CHAPTER 5
Planning for
Environmental
Protection
Many operations in the petroleum exploration and production indus
try have the potential to impact the environment in some way. Because
of the high costs of noncompliance with the numerous regulations
governing the industry and the high costs associated with the loss of
public trust for damaging the environment, substantial resources must
be dedicated to minimizing environmental impact. Because industry
resources are limited, comprehensive environmental protection plans,
including waste management and contingency plans, are needed to
optimize the use of those resources.
One of the first steps in developing environmental protection plans
is to conduct an environmental audit to identify all of the waste
streams at a particular site and to determine whether those waste
streams are being handled in compliance with all applicable regula
tions. Once an audit has been conducted, a written waste management
plan for managing each waste stream should be developed. These plans
identify how each waste stream is to be handled, stored, transported,
treated, and disposed. The plan should also indicate how records are
to be kept. Contingency plans are needed to minimize the impacts of
accidental releases of materials and should incorporate relevant emer
gency responses. Several benefits of environmental audits and waste
management plans are that they:
1. Ensure compliance with applicable environmental laws and
regulations at a reasonable cost.
2. Minimize environmental damage from operations.
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Planning for Environmental Protection
145
3. Minimize short and longterm liabilities and risks associated
with facilities operations.
4. Minimize operating costs through savings in raw materials and
production costs.
5. Minimize personnel costs associated with waste management by
having a written plan available.
6. Minimize costs of treating and disposing of wastes.
7. Minimize employee exposure to potentially hazardous materials.
8. Maintain a favorable corporate image.
Environmental protection plans should be developed with the guid
ance of people who are knowledgeable in the technical, regulatory, and
operational aspects of systems operations and waste disposal. To be
successful, these plans need the visible support of top management
and require the active participation of field personnel, both in develop
ing and implementing them. Because operations, regulations, and
technology are constantly changing, environmental audits should be
conducted periodically and associated waste management and contin
gency plans should be updated as needed.
An assessment of the potential environmental impact from future
developments should also be conducted, and may be required in some
areas. Such assessments include identifying all areas that the develop
ment may impact, quantifying the scale of that impact, and comparing
it to regulatory standards. The findings of this assessment can be used
to improve the design of facilities to reduce associated environmental
risks. The entire project should be reevaluated at regular intervals to
ensure minimal environmental impact (Grogan, 1991).
5.1 ENVIRONMENTAL AUDITS
An important step in developing effective waste management plans
is to conduct an environmental audit. Environmental audits provide
detailed information on the types, volumes, locations, and handling
procedures of all materials that have a potential to impact the environ
ment, and they determine whether operations are in compliance with
applicable regulations. The primary objectives of environmental audits
are to lower the operating, compliance, and liability costs associated
with drilling and production operations. Several benefits of environ
mental audits are that they:
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Environmental Control in Petroleum Engineering
1. Determine compliance with applicable regulations.
2. Identify activities where improvements in operations are needed
to minimize risk, liability, and potential environmental impacts
or to lower operating costs.
3. Improve decisionmaking ability of facility personnel regarding
environmental issues.
4. Provide an early warning device for impending problems and
reduce "surprises" or repeated patterns of shortcomings in
environmental performance.
5. Increase awareness among supervisors and operators of the
regulatory requirements.
6. Reinforce top management's commitment to environmental
protection.
7. Identify areas where environmental training is needed.
8. Establish and quantify measures for risk reduction.
9. Confirm effective communications between environmental staff
and field personnel.
10. Increase confidence of management that environmental activi
ties are a sound investment.
11. Determine how knowledgeable employees are about company
policies regarding environmental issues.
12. Improve relationship with regulatory agencies and the public
in regard to activities conducted by the company.
Normally, the first steps in conducting an environmental audit are
o review records of the site, to interview knowledgeable people about
he site and its activities, and to conduct a physical inspection of the
site. If obvious problems exist or if insufficient information to evaluate
he potential for future liability of the property is available, then a
more detailed study involving sampling and detailed engineering
analysis may be required (Curtis and Kirchof, 1993). The information
hat can be obtained during an audit includes records of all materials
entering the area, including those produced from the wells, created in
surface facilities, and brought into the area by service companies.
These materials include all solids, sludges, liquids, gases, and mixtures.
The volume of each of these materials and their ultimate disposition
must be identified. Naturally occurring radioactive materials (NORM)
generated during production must also be considered.
Planning for Environmental Protection
14?
Environmental audits are normally conducted by a team of one to
about five people, depending on the size and complexity of the facility
being audited. The team members must be familiar with the full range
of issues affecting the facility, including all regulatory and technical
areas. They must have a knowledge of the audit process, understand
all applicable regulations, have an independent viewpoint on the
facility, know corporate policy, and be familiar with the history and
processes used at the facility. Because audits can be viewed with
hostility by those being audited, team members must also have good
communication and professional skills.
The audit team develops the audit protocol, which is a detailed list
of the activities that will be conducted during the audit. The protocol
depends on the needs and objectives of the audit, but normally includes
three steps: preaudit activities, a field visit to the site, and some type
of followup.
In the preaudit activities, the goals and objectives of the audit are
established, the scope, target, and subjects of the audit are selected, a
schedule is developed, checklists and questionnaires are developed,
materials are exchanged between the audit team and targeted facility,
and all exchanged materials are reviewed.
The field visit starts with a briefing in which the purpose, authority,
confidentiality arrangements, facilities, and documents are reviewed.
Managers, foremen, and operations people should all be interviewed
to determine their knowledge about environmental issues and company
policies. The questions asked should be from a prepared questionnaire
developed during the preaudit activities. Detailed records of all permitted
activities are required under most permits and should be reviewed. A tour
of the facilities is then conducted to verify that operations are actually
conducted according to the written plans. A facility visit should include
a walk around the property line to observe possible storm runoff dis
charges. Following the tour, a final briefing is given. The final briefing
should be a very short summary of the audit findings, with a statement
that a formal written report will be forthcoming. This briefing informs
local management of what senior management will be told and gives
them an opportunity to prepare their response.
After the field visit, a final written report is prepared, a list of
corrective measures is developed, and a followup visit to verify the
success of the corrective measures is conducted. The report should
review the program strengths, describe areas where improvement is
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needed, and make recommendations for corrective action to address
problems. In preparing the written report, any problems can usually
be grouped into one of the following three categories:
1. Activities that are in violation of permits or regulations, activities
that are in violation of company policies, or policies that encour
age activities to be in violation. These activities require the
attention of senior management and need immediate correction.
2. Conditions that could result in a violation or in a situation that
could harm the environment. Corrective actions are needed, but
immediate action is not necessarily required. Corrective actions
could be scheduled around site operations.
3. Local issues concerning housekeeping, storage, purchasing, or
similar items. Corrective actions are recommended, but not
necessarily required.
Depending on the magnitude of the problems identified and the
corrective actions recommended, a followup visit should be conducted
within 3 to 12 months after the audit.
Typical operational problems that are identified in environmental
audits are compressors and engines that are installed without state
permits or inventorying; gas plants and sweetening plants that are
installed or modified without considering new source performance
standards [NSPS] or prevention of significant deterioration [PSD]
monitoring, analysis, or control technology; unapproved analytical
methods that are used for determining compliance; and underground
injection wells that have not received the proper permits. Typical
problems with personnel training are field foremen who do not know
if hazardous substances are located at their site or how to report a
release to regulatory agencies if a release occurs, and engineering staff
who are not well informed of environmental design requirements.
One difficulty with performing an internal environmental audit is
that the U.S. Environmental Protection Agency can request a copy of
the audit under certain circumstances. Unless there is a commitment
by top management to correct any and all deficiencies found, the
existence of the audit could leave the company and its employees open
to regulatory action, including criminal penalties for willful violation
of the law for not implementing corrective measures.
A number of case histories on developing environmental audits for
oil and gas production facilities have been published (Guckian et al.,
Planning for Environmental Protection
149
1993; Tan and Hartog, 1991; Jennett, 1991; Whitehead, 1991; and
Crump and O'Gorman, 1991).
5.2 WASTE MANAGEMENT PLANS
Waste management plans identify exactly how each waste stream
should be managed. They ensure that appropriate engineering controls,
proper waste management options, adequate recordkeeping and report
ing systems, and ongoing employee training are in place. The informa
tion obtained from environmental audits can be used in developing a
waste management plan.
One of the first steps in developing a waste management plan is to
identify the region and scope to be covered. All materials generated
within the region must be identified, quantified, and characterized.
These data must include chemical toxicological, health, fire, explosive,
and reactivity information. They should also include first aid proce
dures to be used in the event of human exposure to the material.
Material Safety Data Sheets (MSDS) provide much of this information
and can be obtained from chemical suppliers.
The potential for a material to migrate from a site must also be
considered when determining the best way to manage it. Factors like
topography, hydrology, geology, soil conditions, and the presence of
sources of usable water must be evaluated. Historical rainfall and
distribution data are also needed to determine soil loading conditions,
to predict net evaporation rates, to determine how quickly reserves pits
will dry, and to evaluate overtopping potential of open tanks and pits
during storms. Other factors that must be considered are the special
needs of environmentally sensitive areas such as wetlands, rain forests,
arctic tundra, arctic icepack, areas where subsidence during production
may occur, urban areas, historical sites, archaeological sites, protected
habitats, and sites providing habitats for endangered species.
A critical factor that must also be considered in developing waste
management plans is the regulatory status of each material at a site. One
way to classify wastes in the United States is according to the Resource
Conservation and Recovery Act (RCRA) categories of exempt and nonexempt
wastes (Stilwell, 1991). Nonexempt wastes can be further classified as
hazardous, nonhazardous, or special wastes, as discussed below:
« Exempt wastes are directly associated with drilling of an oil or
gas well or generated from the exploration and production of oil
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Environmental Control in Petroleum Engineering
and gas. Most wastes in the upstream petroleum industry fall into
this classification.
• Nonexempt nonhazardous wastes are not directly associated with
drilling and production activities for oil and gas and are not con
sidered hazardous under RCRA, Subtitle C. Nonhazardous wastes are
those that are not specifically listed as hazardous or that do not fail
the hazardous criteria of reactivity, corrosivity, ignitability, or toxicity.
These criteria are discussed in Appendix A.
• Nonexempt hazardous wastes are either listed or fail the hazardous
criteria of reactivity, corrosivity, ignitability, or toxicity. An
example of these wastes are solvents used to clean production
equipment. Solvents generally fail the ignitability criterion.
• Nonexempt special wastes are covered under special statutes and
regulations. Examples of wastes in this classification are asbestos,
naturally occurring radioactive materials (NORM), polychlorinated
biphenyls (PCBs), and pesticides.
A critical step in developing waste management plans is to identify
a specific action plan for handling each and every material at all sites
covered by the waste management plan. These action plans should be
based on the "Hierarchy of Waste Management Principles" that were
promulgated in the Pollution Prevention Act of 1990 and further
defined by the U.S. Environmental Protection Agency's "Memorandum
on Pollution Prevention" (Habicht, 1992). This hierarchy of waste
management principles defines the preferred order for actions related
to managing wastes.
The first and most important action in the waste management
hierarchy is to reduce the volume of wastes generated. The next action
is to reuse the wastes or materials in the wastes. Only after those
actions have been completed should the remaining wastes be treated
and disposed. By following this hierarchy, both the volume of waste
to be disposed and the ultimate disposal cost will be minimized.
Possible actions for managing each material at a site can be identi
fied by evaluating current practices in that area, current practices in
other areas, current practices for other types of wastes, practices used
by other companies or industries for similar wastes, and new practices
that may be described at trade shows or in the literature. Examples
of waste management actions within the Hierarchy of Waste Manage
ment Principles are given in the following section.
Planning for Environmental Protection
151
Once a list of possible actions has been identified, those actions need
to be evaluated and prioritized and a preferred action selected. Factors to
be considered include cost, practicality, future liability, regulatory status,
availability of resources and facilities, company policy, and local com
munity concerns. Actions that are unacceptable should also be identi
fied. This evaluation can include a risk assessment study to optimize
the use of the available funds (Stanley and Johnson, 1993).
A critical aspect of good waste management plans is to develop and
maintain good bookkeeping practices. This bookkeeping must include
a waste tracking program which identifies where the waste was gener
ated, the date the waste was generated, the type of waste and its
volume, any transportation of the waste, the disposal method and
location, and the contractor employed. A waste management plan must
also identify which personnel are responsible for the proper manage
ment of all wastes produced at the targeted facilities.
A number of waste management plans have been discussed in the
literature (American Petroleum Institute, 1989; Benoit and Schuh,
1993; Canadian Petroleum Association, 1990; Chandler, 1991; Frampton,
1990; Greer, 1991; Huddleston et al., 1990; Jones and Woodruffe,
1991; Manning and Grannan, 1991; Sarokin et al. 1985; Stilwell, 1991;
Yates, 1990). Waste management plans can also be computerized
(Crump and O'Gorman, 1991; Warner, 1993; Lawrence et al., 1993).
Sensitive habitats like rain forests or arctic regions may require special
operating practices to protect them. These practices are dis
cussed in Appendix B.
5.3 WASTE MANAGEMENT ACTIONS
In this section, a number of examples of waste management activi
ties for drilling and production operations are discussed according to
the hierarchy of waste management principles. These activities include
ways to minimize the volume and/or toxicity of wastes generated and
ways to reuse or recycle wastes. Waste treatment and waste disposal
options are discussed in Chapters 6 and 7, respectively.
5.3.1
Waste Minimization
The most effective way to reduce the environmental impact associ
ated with exploration and production of oil and gas is to minimize the
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Environmental Control in Petroleum Engineering
total volume and/or the toxic fraction of wastes generated. The primary
waste minimization activities are to make changes in how chemical
inventories are managed, how operations are conducted, which materials
and chemicals are used, and how equipment is operated.
The advantages of waste minimization include avoidance of waste
transportation and disposal costs, elimination of expensive pollution
control equipment, improved product quality, less administrative
recordkeeping, lower onsite handling costs, a smaller waste storage
area, reduced waste and tax obligations, improved public image, lower
potential environmental impacts, and reduced future liabilities.
Unfortunately, the opportunities to significantly reduce the volume
of drilling and production wastes are limited. The greatest volume of
waste is produced water, which is controlled by the age and production
history of the field. The volume of drilling wastes is controlled primarily
by the depth and number of wells drilled. Nevertheless, many opportuni
ties are available for minimizing wastes and have been described in
the literature (Hall and Spell, 1991; Savage, 1993; Thurber, 1992;
Wojtanowicz, 1993a and 1993b).
Inventory Management
One aspect of waste minimization is to carefully monitor inventories
of all materials at a site. Accurate, written records of all raw and
processed materials and their volumes should be kept for every stage
of handling and production. The costs of each material, including
disposal, should also be recorded.
Better management of materials inventories provides significant
environmental benefits. It allows a material balance to be conducted
on all materials at all stages of usage. A detailed material balance can
help identify where unwanted losses and waste may be occurring.
From a better understanding of actual needs of different materials, the
volumes of chemicals purchased may be reduced. Keeping excess
chemicals in stock increases both the cost and the chance of spillage
or leakage. Accurate records also allow chemicals to be rotated so that
their shelf life does not expire before they are used. If large volumes
of a chemical are needed, it can be purchased in bulk to reduce the
number of containers requiring disposal. Accurate records can be used
to determine whether the volume of chemicals purchased are propor
tional to their use and whether purchase restrictions are needed.
Planning for Environmental Protection
153
Improved Operations
Another important method for minimizing the amount of potentially
toxic wastes generated is to change the operating procedures at the
various sites. Many changes can be made to improve operations at a
relatively low cost, particularly if planned in advance.
New sites can be constructed to minimize environmental risks.
Access roads can be sited to minimize any disruption. Sites should
be kept as small as possible and should be designed so that natural
drainage features will divert rainwater around the site, in particular,
away from the rig and reserves pits. The soil type should be evaluated
to determine if it is suitable for constructing site facilities such as
buildings, drill pads, ponds, levees, or production tanks. Dikes and
catchment basins should be constructed around all storage tanks and
loading areas to contain any leaks and spills. If a site is suspected of
being contaminated by any previous activity, a detailed site assessment
should be conducted to characterize any contamination before any new
activity commences.
All operations should be carefully planned in advance to minimize
the use of materials. Materials storage, handling, and transportation
procedures should be reviewed to minimize losses. Only the required
amount of chemicals and equipment should be available at the site,
A very important step in improving operations is to keep different
types of wastes segregated. Waste streams should never be mixed,
Because the toxicities and regulations vary for different wastes,
keeping the waste streams segregated allows the best disposal options
to be selected for each waste. This minimizes the volume of toxic
wastes that must be handled under the most stringent and expensive
regulations. For example, hazardous and nonhazardous wastes should
never be mixed. Municipal or commercial wastes should be kept
separate from other site wastes. Soil contaminated with hazardous and/
or commercial wastes should be kept separate from soil contaminated
with other wastes. Sites should be designed to keep unwanted materials
from entering the fluid system and reserves pit during drilling. This
unwanted material includes rig wash, pump lubrication water, drill pipe
handling, and stormwater runoff. Levees or ditches can be used around
a site to divert stormwater or contain any spills.
Good housekeeping practices must be observed at all sites. Trash
containers should be provided at drill sites and production facilities
154
Environmental Control in Petroleum Engineering
to discourage disposal of refuse, paper, and other household trash in
pits. These household wastes should be collected and stored separately
for offsite disposal. Sanitary wastes should be collected and treated
to satisfy state and local effluent requirements using septic systems,
portable commercial containers, shipment to municipal sewage facili
ties, or disposal at municipal solid waste sites. Leaks and spills from
all equipment should be eliminated. Liners, drip pans, or basins can
be used to collect any potential spillage from equipment. Equipment
that is leaking should be repaired or replaced. Drilling rigs should be
washed at a site only if absolutely needed and only with recycled pit
or sump water, not with fresh water.
Optimized drilling operations provide a significant opportunity for
minimizing wastes. Because the total volume of drilling wastes is
controlled primarily by the hole size and well depth, the smallest
diameter hole should be drilled to minimize the volume of cuttings
generated and drilling mud used. The needs for future recovery activi
ties, including possible multiple tubing strings for improved recovery
operations, must be considered when determining the hole size. Inter
mediate casing strings can be used to isolate problem zones, e.g., salt,
high pressure, or reactive shales, and minimize the volume of special
ized drilling mud needed to drill below those zones. Hole washout can
be minimized during drilling by limiting the recirculation rate of
drilling fluids such that the annular velocity to lift cuttings is not
excessive. During drilling, the surge and swab pressures in the well
bore should be minimized by limiting rapid pipe movement to maintain
a good mudcake and prevent further hole enlargement.
A number of drilling mud systems are available. Closedloop sys
tems with good solids control and separation equipment can be used
to minimize the volume of drilling wastes. In these systems, covered
steel tanks are used instead of digging reserves pits in the ground.
Advanced solids separation and dewatering equipment must be used,
however. Drilling fluid systems and fluids should be designed to
minimize drilledsolids degradation and reduction of particle size. The
bottom of the mousehole should be cemented to prevent drilling fluids
from leaching into groundwater when the kelly is in place.
Reserves pits can be constructed to minimize the volume of wastes.
They should cover a limited area to control the amount of rainfall
entering them, but they should also have sufficient capacity so they
do not overflow during heavy rains. In many areas, pit liners are
Planning for Environmental Protection
155
required if saltwater or oilbased muds are used. Liners should be
considered in sensitive areas, even if not required by current regula
tions. Netting may be required over pits to prevent birds from landing
in them, particularly if the pits contain floating hydrocarbons.
Because many different fluids are found at most drill sites, a
managed pit system with multiple pits can be used to keep the different
fluids separated (Hall et aL, 1991; Pontiff et al., 1990). For example,
one pit could be used for mud reserves, one for cleaned cuttings, one
for skimmed oil, one for kicks, and one for storm water runoff. If
different mud types are used for different parts of the well, e.g., when
drilling through an overpressured layer, a salt dome, or other very
sensitive formation, a separate pit can be used for each mud type. One
pit can be used for drilling the top section of the well where native
materials can be used with minimal additives and one pit can be used
for drilling through the productive horizon, particularly for horizontal
wells. These systems minimize the total volume of materials having
the greatest potential for environmental impact. With a managed pit
system, different materials can be disposed of in the best way, mini
mizing the volume of materials that must be disposed of at the highest
cost and reducing future liability.
Preplanning is important when developing a mud for each well.
When selecting a mud, detailed questions should be asked to the sales
representative about exactly what the various additives will do and
whether they are actually necessary for a particular well. Mud additives
can be pilot tested in small volumes to ensure they behave as claimed.
Inhibitive mud should be used to minimize hole enlargement during
drilling from the hydration of shales. Mud density changes should be
avoided because these normally require discarding some of the mud
and reformulating the remainder; this leads to an increase in the total
volume of mud that is used.
A number of operational changes during production can also be
implemented to minimize the total volume of waste generated. Routine
inspection and/or pressure testing of all tanks, vessels, gathering lines,
and flow lines should be scheduled. Routine inspection and/or auto
matic pumps should be installed in all sumps.
Unfortunately, the largest volume of production waste is produced
water and little can be done to minimize its production. In some
formations, coning of water can be minimized by dually completing
a well in both the water and oil zone. This can limit water coning
156
Environmental Control in Petroleum Engineering
and reduce the amount of water produced with the oil. The water
produced from the water zone must also be disposed of (reinjection),
but it should contain essentially no oil (Wojtanowicz, 1991). Polymers,
gels, or cement can be used to plug water production zones if they
are separate from oil producing zones.
Since many drilling and production operations are conducted by
contractors, they should be carefully reviewed and selected. Contrac
tors should have a good environmental track record. When conducting
the bidding process for selecting equipment to be used, a visual
inspection of the equipment is advised to determine its general condi
tion, particularly drilling rigs. Contractors should have properly func
tioning equipment, with drip pans and splash guards.
Any contracts should specify activities that are prohibited while the
contractor is on site. Such activities can include unnecessary rig
washing, painting of the contractor's equipment, or changing lube oil
during downtime. This will minimize the probability that excess water,
painting wastes, or used oil gets dumped into reserves pits. An envi
ronmental activity review should be conducted with all contractor
crews just prior to the start of activities. This review should include
waste handling and minimization procedures.
Materials Substitution
Another important method for minimizing the amount of potentially
toxic wastes generated is to use less toxic materials for the various
operational processes. A number of studies of material substitutions
have been presented (Derkics and Souders, 1993; Freidheim and
Shinnie, 1991; Peresich et al, 1991; Savage, 1993; Thurber, 1992;
Wojtanowicz, 1991).
Drilling muds represent a significant opportunity for toxic waste
reduction by materials substitution. When substituting materials,
however, it is important to ensure that the substituted materials yield
a drilling mud that still has acceptable properties.
One of the best opportunities for materials substitution is in wells
where oilbased muds are needed. Two alternatives to the use of diesel
oil as a base fluid are being studied: using a less toxic oilbased mud
and using a waterbased mud with an improved additives package.
These alternative mud systems, however, are considerably more expen
sive than traditional muds. Unfortunately, the use and discharge of
Planning for Environmental Protection
1SI
hese new drilling muds may still be prohibited, even though they
provide significantly improved environmental protection. Many of the
egulations covering the discharge of drilling muds were established
before the development of these alternative mud systems and have not
been changed to reflect these new technologies.
One way to lower the toxicity of diesel oil muds is to increase the
amount of water in the mud emulsion. This will reduce the amount
of oil that is available to be retained on cuttings. Water contents in
new mud formulations have been reported to be as high as 65%
(Friedheim and Shinnie, 1991). Traditional muds have water contents
ypically around 10% or less. Another way to lower the toxicity of
oilbased muds is to use a less toxic base oil. Mineral oils having a
ow concentration of aromatic hydrocarbons have been successfully
used (Jacques et al., 1992), as have esters, ethers, and polyalphaolefins
(Peresich et al., 1991; Candler et al., 1993). Cationic surfactants can
also be added to the mud to reduce the amount of oil trapped on
cuttings (Friedheim and Shinnie, 1991).
A variety of new waterbased muds are being developed as possible
substitutes for oilbased muds. The additives for these muds have
ncluded various lowtoxicity polymers and glycols (Bland, 1992;
Bleter et al., 1993; Enright et al., 1991; Reid et al., 1993). Substitu
ions can also be made with the additives used in waterbased rnuds.
For example, dolomite can be used instead of barite as a weighting
agent. Additives made from watersoluble combinations of silicon,
phosphorus, aluminum, and boron can replace some conventional
additives (Zakharov and Konovaiov, 1992). New pipe dopes are being
developed that do not contain heavy metals; these new pipe dopes have
ncluded micronsized aluminaceramic beads in a lithium grease.
Drilling muds can be reformulated to improve shale stability. This
will reduce wellbore washouts, minimize the degradation of solids (the
breaking into smaller, hardertoseparate particles), reduce the amount
of material brought to the surface to be handled, and lower the mud
volume requirement of the well (Alford, 1991; Thurber, 1992). Potas
sium acetate or potassium carbonate can be used instead of potassium
chloride for shale stability problems to minimize the chloride content
of the drilling mud (Gillenwater and Ray, 1989). Other mud additives
and suggested substitute materials are given in Tables 51 and 52.
A variety of opportunities are available during production operations
o substitute less toxic materials for more toxic, traditional materials. For
a
crr
zyxwvutsrqp
Table 5-1
Substitute Materiafs for Drilling Fluid Additives
_.
Additive
Toxic Component
Use
Substitute Material
Chrome lignosulfonate/
lignite
Sulfomethylated
Chromium
Deflocculant
Chromium
Deflocculant
Polyacrylate andfor
polyacrylamide polymers
Polyacrylate and/or
tanninldichromate
Sodium chromate
Zinc chromate
Pentachlorophenol
Chromium
Chromium
Pentachlorophenol
Corrosion controi
W,S control
Biocide
polyacrylamide polymers
Sulfites, phosphonates. and amines
N o ~ ~ h r o m H,S
i u ~ scavengers
Tsothiazolins, carbamates, and
3
N
2.
3
rs
sa
5
Paraform aldehyde
Formaldehyde
Arsenic
Arsenic
Leadbased pipe dope
Barite
Lead
Cadmiumlmercuryl
bariudlead
Source: ufrer T ~ u 1992.
~ ~ e ~
Copyright SPE, with permission.
gluteraldehydes
Biocide
I sothia~olins,carbanla te s , and
gluteraldehydes
B iocide
fsothiazdins, carbamates, and
gluteraldehydes
Pipe thread sea~ant/Iubri~ant Unleaded pipe dope
Mud densifier
Chose barite from sources low
in cadmium, ~ e r c u r yand
~ lead.
s.
3
z
5
s.
7
Y
z
3
2
x
3
9
a
h.
3
rc
a
3.
x
h
Planning for Environmental Protection
159
Table 5-2
Additional Substitute Materials for Drilling Fluid Additives
Hazardous Item
Substitute
Pipe dope compounds: lead, zinc,
copper, and cadmium
Lithiumbased grease with
microsphere ceramic balls
Oils and greases: aromatics, sulfur
White oils manufactured from
highly refined mineral oils
approved for use in the food
industry
Cleaning solvents: varsol, freon,
MEK, phosphate soaps
Citrusbased solvents, high pressure
hot water, jet washers, closedloop
recycling
Source; after Page and Chilton, 1991,
Copyright SPE, with permission.
example, organic cations can be used as a low salt concentration, tempo
rary clay stabilizer in well service fluids (Himes, 1991; Himes et aL,
1990). Zinc, sulfite, or organic phosphate corrosion inhibitors can be used
instead of chromate inhibitors. Pentachlorophenols and formaldehyde
releasing biocides can be replaced with isothiazoline or amines. Petroleum
and alcoholbased defoamers can be replaced with polyglycols.
Opportunities for materials substitution are also available during
related site operations. For example, less toxic detergents can be used
o wash rigs. A better solution, however, is for contractors to install
closedloop washwater systems for washing rigs at their own sites
rather than at the wellhead (Whitney and Greer, 1991). Whenever
possible, unleaded waterbased paints and nonsolvent paint removers,
cleaners, and degreasers can be used. Disposable brushes can be used
o eliminate the need for paint thinners and solvents, although the
brushes must then be disposed of. Waterbased dyes can be used
nstead of trichloroethanebased penetrants when inspecting pipes for
cracks. Substitutes can be used for halon gases in fire suppressants.
Equipment Modifications
Another important method for minimizing the volume of potentially
oxic wastes generated is to ensure that all equipment is properly
160
Environmental Control in Petroleum Engineering
operated and maintained. Inefficient equipment should be replaced with
newer, more efficient equipment.
One of the first steps to be taken is to eliminate all leaks and spills from
equipment. Drip pans can be used beneath the drilling rig floor to catch
all water or mud drained from it. Flexible hoses can be used to drain water to
or from the cellar. Leaking stuffing box seals should be replaced or new
stuffing boxes installed. Fugitive emissions from leaking valves, flanges,
and such fittings can be minimized by replacing leaking equipment.
If the interval between lube oil changes on diesel engines is lengthened,
the volume of waste lube oil can be reduced. The interval recom
mended by manufacturers is normally based on "worst case" conditions
operations. By monitoring the quality of the lube oil over time and
using a higher quality lube oil, it may be possible to increase the time
between changes without any loss of engine protection. This could
significantly reduce the total amount of lube oil used (Reller, 1993).
Internal combustion engines should be properly tuned and the proper
fuel should be used. The emission of partially burned hydrocarbons
can be minimized by control of the fuel/air ratio during combustion.
The formation of SOx during combustion can be minimized by using
a low sulfur fuel such as natural gas.
If the volume of waste generated cannot be sufficiently reduced with
the existing equipment, newer equipment should be installed. Important
environmental features of newer equipment should be how easy they
are to monitor and clean up, as well as how they facilitate waste
recovery and recycling. New equipment should have modern emission
controls. In some cases, equipment with automated process controls
can be installed to ensure optimal operations.
Automatic shutoff nozzles and lowvolume, highpressure nozzles
should be installed on all hoses on the rig floor and wash racks to
minimize wastewater. Water meters should be installed on all fresh
water sources to monitor and control water usage. Rig wash should
be limited to only the minimum needed for safety, not for esthetics.
More efficient separations equipment should be used to separate
solids, hydrocarbons, and water. Newer shale shakers can be used that
are better at filtering out small solids than older equipment. Low shear
pumps should be used for produced water to prevent hydrocarbon
droplets from decreasing in size, because small droplets are more
difficult to remove. Improved backwash equipment and better pro
cedures can be used to extend filter life.
Planning for Environmental Protection
161
The most important way to reduce the emission of volatile hydro
carbons at production facilities is to install vapor recovery systems.
Casing vapor recovery systems should be in thermal recovery opera
tions to collect casing gases. Recovery units can be installed to collect
glycol reboiler vapors (Choi and Spisak, 1993; Schievelbein, 1993).
Mercury manometers along gas flow lines can be replaced with elec
tronic, digital flow meters
5.3.2
Material Reuse
Many of the materials in drilling and production waste streams can
be used more than once. If materials are intended for future use, they
are not wastes. The following materials have a potential for reuse:
acids, amines, antifreeze, batteries, catalysts, caustics, coolants, gases,
glycois, metals, oils, plastics, solvents, water, wax, and some hazard
ous wastes.
Water has a considerable potential for reuse. For example, water
from reserves pits can be used to wash shale shakers and other solids
control equipment during drilling. Reserves pit water should also be
used as makeup water for drilling mud as much as possible. Water
from mud can be cleaned and used as rig washwater. Rig washwater
can be collected and reused, particularly at contractor facilities.
Lubrication and cooling water used by pumps can also be recycled.
Water obtained from dewatering a reserves pit could be treated and
used at another site, particularly in arid areas. Produced water, after
treatment, can be reinjected for pressure maintenance during water
floods or for steam injection in heavy oil recovery.
Material reuse can be facilitated by installing equipment that allows
reuse. For example, closedloop systems can be installed so that
solvents and other materials can be collected and reused in plant
processes. Reusable lube oil filters can be installed in some applica
tions instead of throwaway filters. Flared natural gas can be reinjected
for pressure control, or an alternate use for it can be found. Flaring
should be restricted to emergency conditions only.
Many drilling and production wastes could be used at other sites
or be returned to the vendor. For example, reconditioned drilling mud
could be reused for other wells, either by the operating company or
by the vendor. Waste rnud from one well can be used for plugging or
spudding other wells. Some used chemical containers can be returned
162
Environmental Control in Petroleum Engineering
to the vendor for refilling. Oily rags can be cleaned and reused. Used
drilling mud can also be used to make cement. Waste acids can be
used to neutralize caustic wastes, and vice versa.
Many wastes can be used as feedstock by other companies. Mate
rials exchanges are available in numerous locations to assist companies
in finding other companies that may be interested in obtaining wastes.
These exchanges should be contacted to see exactly what materials
can be recycled in each area. Care should be taken, however, that the
recycler is reputable and in compliance with all regulations. Transfer
of a waste to a waste exchange does not necessarily relieve the waste
generator of future liability for what the waste exchange does with
the waste. A list of some of the major waste exchanges in the United
States is given in Appendix C (Quan, 1989).
In some cases, only part of a particular waste stream contains
valuable materials that can be reused. It may be possible to recover
or reclaim the valuable materials, reducing the net volume of waste.
For example, crude oil tank bottoms, oily sludges, and emulsions can
be treated to recover their hydrocarbons. Oily materials can also be
burned for their energy content. Gravel and cuttings can be washed
and used in construction of roads and other sites.
Companies can take proactive action to assist employees in finding
suitable opportunities for recycling. For example, funds generated from
recycling can be placed in an employee fund for use at employee
discretion to encourage recycling. Emphasis can also be placed on
purchasing recycled goods to increase the market for them.
5.3.3
Treatment and Disposal
Wastes that cannot be eliminated must be treated and disposed.
Treatment is used to reduce the volume and/or toxicity of wastes
and/or put it in a form suitable for final disposal. A number of
treatment and disposal options are available for the wastes generated
in the petroleum industry. These options are discussed in Chapters 6
and 7, respectively.
5.4 CERTIFICATION OF DISPOSAL PROCESSES
One option for waste management is to ship wastes to an offsite,
commercial waste disposal facility. Paying a disposal facility to take
Planning for Environmental Protection
163
wastes, however, does not necessarily remove liability for what subse
quently happens to those wastes. Because the company that generated
the wastes normally retains liability, great care should be exercised
in selecting and using commercial waste disposal facilities. One way
to minimize the risk of liability after custody of the waste has been
ransferred is to develop a formal certification process (Steingraber et
al., 1990).
The first step in the certification of a waste disposal facility is to
gather as much information about the facility as possible. This infor
mation includes institutional information, which includes its conform
ance record for existing rules and regulations, its operational and
physical capabilities, and the geologic and hydrologic conditions at the
site. A detailed site visit should also be conducted. A set of criteria
for deciding whether a facility is acceptable or not must also be
developed. If a facility has been certified to be acceptable and wastes
are shipped to it, the facility should be reevaluated on a regular basis.
Part of the certification process for offsite disposal of wastes is
an evaluation of how the wastes are transported to the facility. Reput
able haulers that have all necessary permits for waste transportation
must be selected. Manifests of all materials shipped are also required
o maintain a paper trail on the disposition of the wastes.
5.5 CONTINGENCY PLANS
Contingency plans are needed to prepare a facility to minimize the
mpact of any foreseeable emergency. Contingency plans for environ
mental protection outline the response of all personnel to an accidental
release of materials that can impact the environment. These plans
describe ways to eliminate the source of the release, to assess the
character, amount, and extent of the release, to identify ways of
containing the release so any impacts are minimized, to recover all
ost or contaminated materials, and to notify relevant regulatory
authorities. Contingency plans must carefully and completely document
he response of all personnel in the event of an emergency (Tomlirt
and Snider, 1994).
Contingency plans supplement, but do not replace, waste manage
ment plans. They provide a framework to prepare for and handle all
significant risk scenarios. Like all waste management plans, contin
gency plans should be in writing. A contingency plan must be accepted
1S4
Environmental Control in Petroleum Engineering
by those with authority to approve or deny its implementation. Prior
review and approval of such a plan by regulatory agencies will help
in obtaining final approval when an emergency occurs. Prior review
and approval, however, does not necessarily mean final approval will
be given to implement the plan in an emergency.
Contingency plans can be developed through the following steps
(Geddes et al., 1990).
Step 1: Identify potential emergencies and complications. All possible
emergencies and complicating factors are to be identified. All
scales of emergencies should be considered.
Step 2: Identify risks and consequences. In this step, the potential
impacts of emergencies on human life, wildlife, and the envi
ronment are determined.
Step 3: Identify resources and capabilities. This step requires a detailed
assessment of all resources available to meet any emergencies.
Resources to be evaluated include personnel, equipment, sup
plies, and funds.
Step 4: Determine and define roles and responsibilities. The actions
of all personnel during an emergency, including field hands,
management, and regulatory agencies, are outlined. Com
munication channels are also clearly explained.
Step 5: Determine response actions. A realistic, detailed plan of action
is outlined for each potential emergency. It should include the
estimated timing of equipment arrival, operations of the equip
ment (including operating personnel), and decisionmaking
priorities.
Step 6: Write and implement the plan. The plan should be written in
easytounderstand language and should be userfriendly. It
should allow for updates and modifications. It should be
considered a "live" plan, i.e., it should be changed as needs
and experience dictate. It is important for the surrounding
community to be informed of the plan and to have input into
it as it is developed and modified.
A number of contingency plans are required in the United States
by federal regulations. For example, the Clean Water Act requires
that spill prevention control and countermeasure (SPCC) plans be
developed to minimize the risk of accidental discharge of oil. The Oil
Pollution Act requires a response plan for actions following the
Planning for Environmental Protection
165
accidental release of oil. The Occupational Safety and Health Admin
istration's "Hazardous Waste Operations and Emergency Response"
(HASWOPER) requires a plan to protect worker health and safety in
cleanup operations at waste sites.
5.6 EMPLOYEE TRAINING
For any environmental protection plan to be effective, it must
be understood and accepted by those who must implement it. Best
results are normally obtained by establishing a formal training program
for all employees who make decisions that can impact the environ
ment. Once developed, environmental protection plans will serve as
handy guides for all the people to use in making the best decisions
regarding wastes.
A critical step in the effective implementation of the environmental
protection plan is to identify the people involved with the actual
decisions impacting the environment and to effectively communicate
the plan to them. Employees need easy access to information on
approved methods for handling, treating, and disposing of different
waste streams, as well as applicable regulations. In many cases, the
first and secondline production and drilling supervisors will be the
primary users of the plan. It is important that they are provided clear,
concise directives on what is required of their operations. These
directives should include appropriate background information.
Because different operations within a company have different needs,
it may be necessary to have a series of separate plans and training
programs to meet those diverse needs. For example, managers, engi
neers, field foremen, and pumpers need different information to
complete their tasks. A onepage summary can be prepared for use in
the field that gives a quick reference on how each waste is to be
handled. This page can be incorporated into a plant operator's or
pumper's field book and posted on bulletin boards. A detailed manual
giving more complete information should be prepared and kept as a
reference manual in various offices. One such reference manual is
available from the Canadian Petroleum Association (1990).
When the plan is written, it is important that it be composed so the
field people can easily understand it, i.e., it must be userfriendly. To
ensure readability, the plan and the manuals should be reviewed by
field personnel before being adopted. Compliance with the plan by
186
Environmental Control in Petroleum Engineering
field personnel will be enhanced by having them contribute to it during
its formulation and development. The plan must also be reviewed and
approved by the management and legal staff of the company.
Once the plan has been written and approved, an effective training
program should be implemented to educate company personnel on its
contents. This program should include adding environmental issues to
ob descriptions and including environmental compliance during job
performance evaluation for promotion and merit salary increases.
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Benoit, J. R. and Shuh, M. G., "Waste Minimization at Sour Gas Facilities,"
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Candler, J. E., Rushing, J. H., and Leuterman, A. J. J., "SyntheticBased Mud
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Chandler, J., "Environmental Rules Make Scrutiny of Rig Work Practices a
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Crump, J, J. and O'Gorman, T. P., "A Task Management System for Com
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Curtis, B. W., II, and Kirchof, C. E., Jr., "Purchase/Sale of Property: The
Black Hole of Corporate Liability, Ways to Minimize Risk," paper SPE
25957 presented at the Society of Petroleum Engineers/Environmental
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Derkics, I). L. and Souders, S. H., "Pollution Prevention and Waste Minimi
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SPE 25934 presented at the Society of Petroleum Engineers/Environmental
Protection Agency's Exploration and Production Environmental Conference,
San Antonio, TX, March 710, 1993.
Enright, D. P., Dye, W. M., and Smith, F. M., "An Environmentally Safe
WaterBased Alternative to Oil Muds," SPE Drilling Engineering, March
1992, pp. 15–19.
Friedheim, J. E. and Shinnie, J. R., "New OilBase Mud Additive Reduces
Oil Discharged on Cuttings," paper SPE/IADC 21941 presented at the
Society of Petroleum Engineers 1991 Drilling Conference, Amsterdam, The
Netherlands, March 1114, 1991.
Frampton, M. J., "Waste Management Decision Making Procedure at Prudhoe
Bay, Alaska," Proceedings of the U.S. Environmental Protection Agency's
First International Symposium on Oil and Gas Exploration and Produc
tion Waste Management Practices, New Orleans, LA, Sept. 10–13, 1990,
pp. 1071–1080.
Geddes, R. L. Fraser, I. M., and Berezuk, Z. L., "Contingency Plans for
Beaufort Sea Drilling into the 1990s," paper CIM/SPE90140, presented
at the Canadian Institute of Mining International Technical Meeting,
Calgary, Alberta, June 1013, 1990.
Gillenwater, K.'E. and Ray, C. R., "Potassium Acetate Adds Flexibility to
Drilling Muds," Oil and Gas J., March 20, 1989, pp. 99102.
Greer, C R., "Managing Environmental Compliance for Field Facilities,"
paper SPE 23510 presented at the Society of Petroleum Engineers First
International Conference on Health, Safety, and Environment, The Hague,
Netherlands, Nov. 10–14, 1991.
Grogan, W, C., "The Use of Environmental Assessments in the Brae Field
Development," paper SPE 23328 presented at the Society of Petroleum
Engineers First International Conference on Health, Safety, and Environ
ment, The Hague, Netherlands, Nov. 1014, 1991.
Guckian, W. M., Hurst, K. G., Kerns, B. K., Moore, D. W., Siblo, J. T., and
Thompson, R. D., "Initiating an Audit Program: A Case History," paper
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SPE 25955 presented at the Society of Petroleum Engineers/Environmental
Protection Agency's Exploration and Production Environmental Conference.
San Antonio, TX, March 710, 1993.
Hail, C. R., Ramos, A. B., Oliver, R. D,, and Favor, J., "The Use of a
Managed Reserve Pit System to Minimize Environmental Costs in the
Pearsall Field," paper SPE 22882 presented at the Society of Petroleum
Engineers 66th Annual Technical Conference and Exhibition, Dallas, TX,
Oct. 69, 1991.
Hall, C. R. and Spell, R. A., "Waste Minimization Program can Reduce
Drilling Costs," Oil and Gas J., July I, 1991, pp. 4346.
Habicht, F. H., "EPA Memorandum on Pollution Prevention" (May 28, 1992),
U.S. Environmental Protection Agency, Bureau of National Affairs, Inc.
Washington, D.C., July 1992.
Himes, R. E., "Environmentally Safe Temporary Clay Stabilizer for Use in
Well Service Fluids," Advances in Filtration and Separation Technology,
Vol. 3, Pollution Control Technology for Oil and Gas Drilling and Production Operations, American Filtration Society. Houston: Gulf Publishing Co.,
1991, pp. 124139.
Himes, R. E., Parker, M. A., and Schmeizl, E. G., "Environmentally Safe
Temporary Clay Stabilizer for Use in Well Service Fluids," paper CIM/
SPE 90142 presented at the Canadian Institute of Mining International
Technical Meeting, Calgary, June 1013, 1990,
Huddleston, R. D., Ross, W. A., Benoit, J. R., "The Development of a Waste
Management System for the UpStream, OnShore Oil and Gas Industry
in Western Canada," Proceedings of the Society of Petroleum Engineers/
Environmental Protection Agency's First International Symposium on Oil
and Gas Exploration and Production Waste Management Practices, New
Orleans, LA, Sept. 1013, 1990, pp. 227242.
acques, D. E, Newman, H. E,, Jr., and Turnbull, W. B., "A Comparison
of Field Drilling Experience with LowViscosity Mineral Oil and
Diesel Muds," paper IADC/SPE 23881 presented at the Society of Petrol
eum Engineers 1992 IADC/SPE Drilling Conference, New Orleans, LA,
Feb. 1821, 1992.
ennett, L. E., "Environmental Audits for Oilfield Service Districts Methodo
logy, Findings, and Recommendations," paper SPE 23489 presented at the
Society of Petroleum Engineers First International Conference on Health,
Safety, and Environment, The Hague, Netherlands, Nov. 3014, 1991.
ones, M. G. and Woodruffe, J. D., "Environmentally Sustainable Economic
Development: E&P Planning in the 1990s," paper SPE 23341 presented
at the Society of Petroleum Engineers First International Conference on
Health, Safety, and Environment, The Hague, Netherlands, Nov. 1014,
1991,
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Lawrence, A. W., Miller, J. A., Miller, D. L., and Linz, D. G., "An Evaluation
of Produced Water Management Options in the Natural Gas Production
Industry," paper SPE 26004 presented at the Society of Petroleum Engineers/
Environmental Protection Agency's Exploration and Production Environ
mental Conference, San Antonio, TX, March 710, 1993.
Manning, L. and Grannan, S. E., "Laboratory WasteManagement Programs
for Research and FieldSupport Operations in the Oilfield Servicing
Industry," paper SPE 23376 presented at the Society of Petroleum Engi
neers First International Conference on Health, Safety, and Environment,
The Hague, Netherlands, Nov. 10–14, 1991.
Page, W. B. and Chilton, C., "An Integrated Approach to Waste Manage
ment," paper SPE 23365 presented at the Society of Petroleum Engineers
First International Conference on Health, Safety, and Environment, The
Hague, Netherlands, Nov. 10–14, 1991.
Peresich, R, L., Burrell, B. R., and Prentice, G. M. "Development and Field
Trial of a Biodegradable Invert Emulsion Fluid," paper SPE/IADC 21935
presented at the Society of Petroleum Engineers 1991 Drilling Conference,
Amsterdam, The Netherlands, March 11–14, 1991.
Pontiff, D., Sammons, J., Hall, C. R., and Spell, R. A., "Theory, Design, and
Operation of an Environmentally Managed Pit System," Proceedings of the
U.S. Environmental Protection Agency's First International Symposium on
Oil and Gas Exploration and Production Waste Management Practices, New
Orleans, LA, Sept. 1013, 1990, pp. 977986.
Quan, B., "Waste Exchanges," in Standard Handbook of Hazardous Waste
Treatment and Disposal, H. M. Freeman (editor). New York: McGrawHill
Book Company, 1989.
Reid, P. L, Elliott, G. P., Minton, R. C., Chambers, B. D., and Burt, D. A.,
"Reduced Environmental Impact and Improved Drilling Performance with
WaterBased Muds Containing Glycols," paper SPE 25989 presented at the
Society of Petroleum Engineers/Environmental Protection Agency's Explor
ation and Production Environmental Conference, San Antonio, TX,
March 710, 1993.
Reller, C. E., "Waste Oil Reduction for Diesel Engines," paper SPE 26012
presented at the Society of Petroleum Engineers/Environmental Protection
Agency's Exploration and Production Environmental Conference, San
Antonio, TX, March 7–10, 1993.
Sarokin, D. J., Muir, W. R., Miller, C. G., and Sperber, S. R., "Cutting
Chemical Wastes—What 29 Organic Chemical Plants Are Doing to Reduce
Hazardous Wastes," INFORM, Inc., New York, 1985.
Savage, L. L., "Even if You're on the Right Track, You'll Get Run Over If
You Just Sit There: Source Reduction and Recycling in the Oil Field," paper
SPE 26009 presented at the Society of Petroleum Engineers/Environmental
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Protection Agency's Exploration and Production Environmental Conference,
San Antonio, TX, March 710, 1993.
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with GlycolCooled Condensers," paper SPE 25949 presented at the
Society of Petroleum Engineers/Environmental Protection Agency's
Exploration and Production Environmental Conference, San Antonio, TX,
March 710, 1993.
Stanley, C. C. and Johnson, P. C, "An Exposure/RiskBased Corrective
Action Approach for PetroleumContaminated Sites," paper SPE 25982
presented at the Society of Petroleum Engineers/Environmental Protection
Agency's Exploration and Production Environmental Conference, San
Antonio, TX, March 710, 1993.
Steingraber, W. A., Schultz, F., and Steimle, S., "Mobil Waste Management
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Production Waste Management Practices, New Orleans, LA, Sept. 1013,
1990, pp. 599–610.
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Operations," J. Pet. Tech., Jan. 1991, pp. 6771.
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Netherlands, Nov. 1014, 1991.
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Planning for Environmental Protection
171
presented at the Society of Petroleum Engineers 1991 Drilling Conference,
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CHAPTER 6
Waste Treatment
Methods
During drilling and production activities, many wastes are generated
that must be treated. The purpose of waste treatment is to lower the
potential hazards associated with a waste by reducing its toxicity,
minimizing its volume, and/or altering its state so that it is suitable for a
particular disposal option. For many wastes, treatment is required prior
to final disposal. A variety of treatment methods are available for most
wastes, but not all methods can be used on all waste streams. The
different treatment methods vary considerably in effectiveness and cost.
Most waste treatment processes involve separating a waste stream
into its individual components, e.g., removing dissolved or suspended
hydrocarbons and solids from water or removing hydrocarbons from
solids. In many cases, a series of methods may be needed to obtain
the desired treatment levels (Schmidt and Jaeger, 1990).
This chapter describes a variety of processes to treat water and
solids for subsequent reuse or disposal. It also describes treatment
processes for various air pollutants. More detailed discussions of
treatment and disposal methods are available in the literature (Freeman,
1989; Tchobanoglous and Burton, 1991; Canadian Petroleum Associa
tion, 1990; Jones and Leuterman, 1990; Wojtanowicz, 1993).
6.1
TREATMENT OF WATER
A number of methods are available to treat contaminated water to
prepare it for reuse or disposal. The contaminants in water most
commonly encountered in the petroleum industry can be grouped into
two broad categories: hydrocarbons and solids. These contaminants can
be either suspended or dissolved as discussed below.
172
Waste Treatment Methods
6.1.1
173
Removal of Suspended Hydrocarbons
Suspensions of oil droplets in water (emulsions) can be difficult to
separate because they can be stabilized by the interfacial energy
between the oil droplets and the continuous water phase. A variety of
methods are available to remove suspended droplets from water. These
methods consist primarily of variations of gravitational separation,
filtration, or biological degradation.
Gravity Separation
The first step in the removal of hydrocarbons from water is norm
ally gravity separation. Through properly selected separator tanks with
skimmers, most free oil and unstable oil emulsions can be separated
from the water. Gravity separation is usually the simplest and most
economical way to remove large quantities of free oil from water.
However, more advanced methods are normally required to separate
stable emulsions.
The first stage of gravity separation is to pass the water through
large tanks to allow the phases to separate. These tanks are commonly
called free water knockouts, wash tanks, settling tanks, or gun barrels.
The effectiveness of these tanks depends on the droplet size and how
long the water is in the tank (Arnold and Koszela, 1990; Arnold, 1983;
Powers, 1990 and 1993). A schematic of a horizontal separator is
shown in Figure 61.
Mist Eliminajtor
__. _
^
Gas Out
Inlet
Oil
V
Water
u
Water Out
Figure 6-1. Schematic of a horizontal separator.
174
Environmental Control in Petroleum Engineering
Plate separators can be used to improve the separation of oil and
water. These separators consist of a series of closely spaced parallel
plates that allow oil droplets to adhere to the plates, coalesce, and
migrate along them. The closely spaced plates reduce the settling
distance required to separate the oil droplets from the water, Plate
separators are mechanically simple and require little maintenance. They
are relatively large and are not effective for very small oil droplets.
Plate separators can reduce oil concentrations to 225 mg/1, with an
average of 15 mg/1 (Simms et al., 1990), and can remove oil droplets
down to about 2030 micrometers in diameter (Van Den Broek and
Plat, 1991). As summarized in Table 61, plate separators can have
operational difficulties under some conditions.
Hydrocyclones can be used to further separate oil and water. A high
velocity stream is injected tangentially into the conicallyshaped
hydrocyclones, creating a vortex. The radial acceleration created in the
hydrocyclone can be several orders of magnitude greater than that of
gravity, and forces the more dense water to the outer edge of the
hydrocyclone and the less dense oil to the center. The oil is then
produced out of one end of the hydrocyclone and the water out of the
Table 6-1
Operational Problems with Oil Separation Equipment
Gas Flotation
Plate Separators
Hydrocyclones
Plugging of plates
Erosion
Unable to handle emulsions
Unable to handle
emulsions
Corrosion
Level control problems
Platform motion
Sand buildup
Platform motion
Oil slugs
Oil slugs
Surge loads
Poor froth formation
Interference by treatment chemicals
Poor mechanical durability
Scale/sludge buildup
Operator/maintenance intensive
Source: Simms et al., 1990.
Waste Treatment Methods
175
other. The effectiveness of hydrocyclones in separating oil and water
depends on a large number of parameters, including oil droplet size
and oil/water density difference, inlet water velocity, solution gas,
solids, and system geometry (Flanigan et al., 1989; Jones, 1993;
Meldrum, 1988; Smyth and Thew, 1990; Young et al., 1991b), Depend
ing on the conditions, hydrocyclones can reduce oil concentrations to
10 ppm, but 30 ppm is a more common average (Simms et al., 1990),
As summarized in Table 61, hydrocyclones can also have operational
difficulties under some conditions. A schematic of a hydrocyclone is
shown in Figure 62,
Hydrocarbon Outlet
Inlet
Swirl Section
Taper Section
Tail Section
Water Outlet
Figure 6-2. Schematic of a hydrocycione.
176
Environmental Control in Petroleum Engineering
Hydrocyclones for separating oil and water are limited to cases where
the inlet pressure is sufficient to drive the flow (Flanigan et al., 1989).
For lowpressure operations, the fluid may need to be pumped into the
hydrocyclone. A progressive cavity pump with low shear has been found
to be an effective way to increase the fluid pressure without shearing the
oil into smaller drop sizes. The drop size is a critical parameter in the
effectiveness of hydrocyclones in separating oil from water.
A related way to enhance gravity separation is through a decanting
centrifuge. In this device, the produced water enters the spinning
centrifuge, where the oil is separated from the water because of its
lower density. Centrifuges differ from hydrocyclones in that the
spinning is mechanically driven in a centrifuge, while it is induced
by the inlet velocity of the water in a hydrocyclone. A centrifuge can
also have internal plates to enhance separation, making it a spinning
plate separator. Centrifuges can remove oil droplets down to about 2
micrometers in diameter (Van Den Broek and Plat, 1991).
Heater Treaters
Oil and water can also be separated by heating the mixture. The
higher temperature lowers the fluid viscosity of the mixture and alters
the interfacial tension between the phases, allowing the oil and water
to separate faster.
Gas Flotation
Suspended oil droplets can also be removed from water by gas
flotation. If gas bubbles are passed through an emulsion of oilinwater,
the oil droplets will attach to the bubbles and be carried to the top of
the mixture where they can be easily removed. Air bubbles are norm
ally pumped through the water, although the expansion of dissolved
air is also used. Gas flotation is often aided by the addition of chemical
coagulants. Carbon dioxide has also been used as the flotation gas
(Burke et al., 1991). Gas flotation, however, can create a foam that is
difficult to break.
Gas flotation systems can reduce oil concentrations to 15100 mg/1,
with a typical average of 40 mg/1 (Simms et al., 1990). Like other
separation methods, gas flotation systems can have operational difficul
ties, as summarized in Table 61.
Waste Treatment Methods
177
Filtration
One way to remove oil droplets from water is to pass the water
through waterwet filters or membranes. These filter media use capil
lary pressure to trap oil and prevent it from passing out of the filter.
Advanced filtration processes include crossflow membranes such as
microfiltration and ultrafiltration (Chen et al., 1991). These processes
consist of a hydrophilic microfiltration membrane that passes water
(and dissolved material), but not oil droplets. The shape of the filter
is typically a small diameter capillary tube that the emulsion flows
through. A schematic of a microfiltration capillary is shown in Fig
ure 63. The emulsion leaving the tube without passing through the
filter can be recycled through the filter a number of times to further
concentrate the emulsion for other types of treatment or disposal.
Microfiltration processes are usually ineffective for hydrocarbon
removal, however, because the filters and membranes foul easily by
oil and have short useful lifetimes.
Filtration Coalescence
Another type of filtration is to pass the water through oilwet filters.
The oil droplets attach to the filter matrix and coalesce into larger
ones. When the filter medium has become saturated, larger oil drops
will flow out of the filter, either by continued injection or by back
washing. These larger droplets can be more easily removed from the
water by subsequent gravity separation. Sand, gravel, or glass fibers
are common media used for this process.
Filtered water out
Emulsion
I_
I
I
I
III
I
Filtered water out
Figure 6-3. Schematic of a microfiltration capillary tube.
Emulsion
178
Environmental Control in Petroleum Engineering
Chemical Coagulants
The removal of small, suspended oil droplets can be aided by adding
chemicals that coagulate and flocculate the droplets (American Petrol
eum Institute, 1990). These chemicals typically overcome the electro
static repulsion charges on the individual droplets, allowing them to
coagulate into larger drops. These larger drops can then be more
efficiently removed with gravity separation equipment. Common
chemicals used include lime, alum, and polyelectrolytes. The use of
dithiocarbamate has also been reported (Durham, 1993).
Electric Field Separation
Another way to separate oil from water is by applying an electric
field (voltage) to the water to electrostatically remove the oil. These
fields can be applied through either a direct or an alternating current.
Oil droplets in an oilinwater emulsion have a negative surface charge
(zeta potential) that can be manipulated to facilitate their removal.
When a direct current is applied to the water containing such an
emulsion, the oil will migrate toward the positive electrode. The migration
velocity of the drops in many systems is on the order of 1 mrn/min, which
requires separators using very narrowly spaced parallel plates (Fang et
al., 1991). This process, however, can only be used with saline water.
When an alternating current is applied, the droplets may flocculate
if a metal hydroxide is present (Farreil, 1991). This process is known
as alternating current electrocoagulation. In this process, a metal
hydroxide is added to the water and an alternating current is used to
overcome the electrostatic repulsion charges on the particles. When
the electrostatic repulsion charges have been neutralized, the particles
can flocculate and be more easily separated from the water by other
methods. Iron and aluminum hydroxides have been successfully used.
Biological Processes
Biological processes rely on bacterial degradation of hydrocarbons.
They have limited application in the removal of free hydrocarbons
from most wastewater streams in the petroleum industry because they
are too slow and are not appropriate for high oil concentrations. Large
quantities of free oil can limit mass transfer of oxygen and nutrients
Waste Treatment Methods
179
o bacterial colonies that degrade the hydrocarbons. (American Petrol
eum Institute, 1986a). The application of biological processes to other
waste streams will be discussed below.
6.1.2
Removal of Dissolved Hydrocarbons
In addition to suspended hydrocarbons, most produced water also
contains varying amounts of dissolved hydrocarbons. A variety of methods
are available to remove these dissolved hydrocarbons from the water.
Adsorption
An effective way to remove low levels of dissolved hydrocarbons
s to adsorb it onto a solid medium. The most widely used medium is
activated carbon. The pH and temperature of the system impacts the
effectiveness of activated carbon on removing different hydrocarbon
compounds. All free oil must be removed prior to the use of activated
carbon to prevent the oil from clogging the carbon. In some cases,
coal may also be used as an adsorption media. Natural and synthetic
resins have also been developed that have proven effective in removing
dissolved hydrocarbons from water.
Volatilization
Volatile organic carbon compounds (VOCs) can be removed from
water by lowering the partial pressure of the compound in the vapor
n contact with the water. When the partial pressure of the dissolved
VOCs in the water exceeds that of its vapor pressure, the compounds
will come out of solution and enter the vapor phase.
A variety of methods can be used to volatilize VOCs. Perhaps the
most common is air stripping. In this process, air and water are passed
hrough a containment vessel in countercurrent flow where VOCs
evaporate into the air. The removal of VOCs can be enhanced by
heating the air or by using steam, because higher temperatures increase
heir vapor pressure. Volatilization can also be enhanced by pulling a
vacuum on the water, lowering the total system pressure.
One limitation to volatilization is that it transfers the VOCs from
water to a vapor phase, yielding a contaminated vapor stream that must
hen be handled. If air is used, the oxygen will dissolve into the water,
180
Environmental Control in Petroleum Engineering
enhancing any biological degradation of dissolved hydrocarbons remaining
in solution.
Biological Processes
Biological treatment can be used to remove low levels of dissolved
hydrocarbons from wastewater streams. Biological treatment consists
of mixing oxygen and nutrients with the water in a tank. The bacteria
then degrade the organic compounds. This process is widely used in
municipal water treatment plants, but may be too slow for oilfield
applications. Because the high salinity of produced water inhibits
biological growth, biological treatment will not be effective in most
cases. Another limiting factor is the lack of dissolved oxygen for
bacteria. Although oxygen could be added, it would significantly
increase the corrosion rate of the equipment.
Precipitation
The solubility of many organic molecules decreases as the pH
decreases. By lowering the pH, some organic materials can be precipi
tated. Precipitation, however, will not remove all dissolved hydro
carbons and will acidify the water.
Ultraviolet Irradiation
The use of ultraviolet radiation (including solar radiation) to break
down hydrocarbons has also been studied (Green and Kumar, 1990).
In this process, highenergy, shortwavelength photons are used to
break the chemical bonds of dissolved hydrocarbons. When combined
with heating to high temperatures, e.g., by solar collection panels,
virtually complete destruction of hazardous hydrocarbon molecules in
water has been observed. This method may have potential for treating
some hazardous chemicals, but is probably too expensive for treating
oilfield waters.
Oxidation
Dissolved hydrocarbons can also be destroyed through oxidation.
Ozone, peroxide, chlorine, or permangenate have been tested. To be
Waste Treatment Methods
181
effective, however, oxidation normally must be conducted at high
emperatures or with ultraviolet irradiation. Oxidation is not practical
or most oilfield applications.
6.1.3 Removal of Suspended Solids
During many drilling and production activities, solids will be
suspended in water that must be removed prior to water disposal.
These solids include cuttings generated during drilling and sand and
clay particles produced during oil production. Several methods are
available for removing these suspended solids from the water.
Gravity Separation
The simplest way to separate the larger solid particles is to use
gravitational settling. Fluids can be discharged into pits or tanks, where
he solids settle to the bottom. Gravitational settling, however, is not
effective for very small particles. The use of settling pits may also be
imited by environmental regulations and the potential for future
iability. Centrifuges can be used for enhanced gravitational separation.
Filtration
Another way to remove suspended solids is to filter the water. The
water passes through the filter, while the solids are retained. The
esulting filter cakes may be nonhazardous and could be disposed of
ike pit bottom sludge. Filtration has considerable promise for separat
ng oil field wastes (Townley et al., 1989).
Coagulation
An effective way to enhance the separation of suspended particles
s to coagulate (flocculate) the particles into larger agglomerations. The
arger agglomerations can then be separated more easily by gravita
ional settling, centrifugation, or filtration.
One successful way to coagulate suspended solids is to add chemi
cals that overcome the electrostatic repulsive charges on the solids to
allow them to flocculate. Chemicals that can be used include calcium
chloride, ferric chloride, or aluminum potassium sulfate (Hinds et al.,
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Environmental Control in Petroleum Engineering
1986). A high molecular weight polyaerylamide polymer has been
found to be effective to flocculate solids in waterbased drilling muds,
and a nonionic polyethylene oxide with a high molecular weight
nonionic polyacrylamide polymer has been found to be effective for
oilbased muds (Sharma and Smelley, 1991), Chemically enhanced
centrifugation has been successfully used to remove solids from both
drilling mud and produced water (Malachosky et al., 1991).
Suspended solids can also be flocculated with alternating current
eiectrocoagulation (Farrell, 1991). In this process, a metal hydroxide
is added to the water and an alternating current is used to overcome
the electrostatic repulsion charges on the particles. Iron and aluminum
hydroxides have been successfully used.
6.1.4
Removal of Dissolved Solids
Most wastewater also contains dissolved solids, particularly salt,
hardness ions (calcium and magnesium), and heavy metals. A variety
of methods are available to treat these waters. The methods vary
considerably in cost and effectiveness,
Ion Exchange
Ion exchange (water softening) is an effective way to remove
hardness ions from water. In most cases, the hardness ions (calcium
and magnesium) are replaced with sodium ions. The removal of
hardness ions is necessary for many processes because these ions
readily precipitate and form a hard scale that can foul equipment.
There are two major ion exchange resins (substrates) that are
commonly used: strong acid resins, using sulfonic acid, and weak acid
resins, using carboxylic acid. Strong acid resins can be regenerated
simply by flushing with a concentrated solution of sodium chloride.
Weak acid resins, however, must be regenerated by flushing with a
strong acidlike hydrochloric or sulfuric and then neutralizing with
sodium hydroxide.
In some cases, the water can simply be passed through a bed of
clay particles. The cation exchange capacity of most clays is very high,
which allows them to trap and retain relatively high concentrations of
dissolved metals. Activated alumina filtration is also an effective ion
exchange media for metals like lead, mercury, and silver.
Waste Treatment Methods
183
Precipitation
Many dissolved solids precipitate from water to form scale as the
temperature, pressure, and/or chemistry changes. The most widely used
system for precipitation is to add lime (CaOH) or sodium hydroxide
(NaOH) to increase the pH of the water. At high pHs, dissolved solids,
including heavy metals, tend to precipitate as a hydroxide sludge. Lime
plus sodium carbonate can also be used to enhance the precipitation
of calcium carbonate. The pH at which many metal hydroxides will
precipitate is shown in Table 62.
Precipitation of some dissolved solids, particularly calcium and
radium, can be enhanced by allowing the water to flow in channels
open to the atmosphere (Caswell et al., 1992). Dissolved heavy metals
can also be flocculated with organic materials to form colloids. These
colloids can then be removed from the water as a suspended solid.
Most forms of precipitation, however, leave residual levels of solids
dissolved in solution. These residual levels may still exceed regulatory
standards, and additional treatment of the water may be required.
Table 6-2
Precipitation of
Metal Hydroxides as
a Function of pH
Metal
pH
AP
Cd2+
Co2+
Cr3+
Cu 2+
Fe2+
Fe3+
Hg2+
Mn 2+
Ni 2+
Pb2+
Zn 2+
4.1
6.7
6.9
5.3
5.3
5.5
2.0
7.3
8.5
6.7
6.0
6.7
Source: Dean et al., 1972,
Copyright 1972, American Chemical
Society. Reprinted with permission.
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Environmental Control in Petroleum Engineering
Reverse Osmosis
The most common way to totally remove all dissolved solids from
water is through filtration processes like reverse osmosis. These pro
cesses, however, are not intended to be used for waste water treatment,
but to provide potable water from nonpotable water. For example,
reverse osmosis is commonly used to provide drinking water from
seawater in desalinization plants. During reverse osmosis, saline water
is pumped through a very small pore filter. The water molecules pass
through the filter, but the larger dissolved solids molecules do not.
Although the water supplied by a reverse osmosis plant is pure enough
to be used for most purposes, the dissolved solids concentration in the
waste stream that does not pass through the filter is higher than before
and must still be disposed. Fouling is the most difficult problem to
overcome when using reverse osmosis on oilfield brines. Pretreatment
of the water prior to entering the reverse osmosis facility is required.
Because of its high cost, reverse osmosis is most commonly used
to provide a supply of pure water in arid areas, rather than as a
treatment method for wastewater. However, in areas where highquality
water is scarce, reverse osmosis can be used to treat produced water.
(Tao et al, 1993).
Evaporation/Distillation
Another way to obtain potable water from water containing impuri
ties is to evaporate and condense the water. Like reverse osmosis, this
process is primarily used to provide a stream of pure water, not to
treat a stream of wastewater. Like reverse osmosis, this process
concentrates the wastes, which results in a smaller waste volume that
ultimately must be disposed. This process is also very expensive.
Biological Processes
Although biological processes cannot destroy dissolved solids, they
can alter their chemical form. For example, biological processes can
alter the availability of heavy metals for uptake by plants, as well as
the ability of metals to leach through the soil (Canaratto et al., 1991).
Bacterial remediation has also been successfully used to remove
sulfides from produced water (Sublette et al., 1993).
6.1.5
Waste Treatment Methods
185
Neutralization
Many aqueous wastes in the petroleum industry are either acidic
or alkaline. These wastes often must be treated to neutralize their
reactivity before reuse or disposal. In many cases, the simplest treat
ment method is to mix these types of wastes for mutual neutralization.
Because mixing may result in an exothermic reaction, it must be done
with care to minimize any safety hazards.
6.2 TREATMENT OF SOLIDS
During drilling and production activities, a substantial volume of
contaminated cuttings, soil, and produced solids are generated. The
most common treatment method is to separate the solids from any
contaminating water and/or hydrocarbons.
A variety of treatment methods are available to clean contaminated
solids and are reviewed below. The effectiveness of different treatment
methods depends on the solid type and size, as well as the initial
contamination level and targeted final contamination level. Prepro
cessing techniques, including materials handling, can also impact the
effectiveness of a treatment method. Preliminary tests of a particular
method on a representative sample are recommended.
6.2.1
Removal of Water
A variety of methods are available to remove water from solids,
including evaporation and filtration. One of the most common applica
tions of dewatering technology is treating reserves pits containing drill
cuttings and waterbased drilling muds.
Evaporation
The simplest way to dewater solid wastes in arid climates is to put
them in open pits or on concrete pads and allow the free water to
evaporate. Evaporation is a common way to remove water from
reserves pits following drilling, although changes in regulations may
now require a more rapid dewatering than evaporation allows. Pro
duced water can also be disposed of by evaporation, as long as the
volumes are relatively low (Mutch, 1990).
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Environmental Control in Petroleum Engineering
In most cases, no special attempt has been made to limit leaching
of metals or hydrocarbons from reserves pits or evaporation ponds. If
eaching is a problem, the pit can be constructed with an impermeable
liner and a leachate collection system with monitoring wells and
enhanced evaporation features (sprinkler recirculation to increase the
surfacetovolume ratio of the water). Lined pits are now required in
some areas for oilbased or salty drilling mud systems. Any sus
pended or dissolved solids in the water will be concentrated as the
water evaporates. If the pond has completely dried, these materials
will be converted into a sludge, which may require further treatment
before disposal.
Before dewatering and closure of reserves pits, the pit contents can
segregate into layers. These layers can include a layer of free oil
floating on a layer of water. The water normally contains a high
concentration of dissolved solids. At the bottom is a layer of sludge
hat contains most of the settled solids. As the oil layer is weathered,
a surface crust can also form. These top layers inhibit the evaporation
of water, delaying the natural dewatering of the pits.
Percolation
In some arid areas where the water table is very deep, aqueous
wastes can be placed in percolation ponds. These ponds have perme
able sides and bottoms, allowing the water to percolate into the
surrounding soil, leaving the solids at the bottom of the pond. The
use of these ponds is highly restricted, however, because they allow
dissolved solids in the water to spread into the surrounding soil.
Mechanical Methods
In many cases, evaporation is too slow to remove water from solid
wastes. A number of mechanical methods are available to dewater
solids. Preliminary separation of free liquids from the solids should
be made with shale shakers, settling ponds, or hydrocyclones.
To further reduce the free water content of sludges, more advanced
and expensive) technologies can be used. These technologies include
highpressure filter presses, centrifuges, and vacuum filtering. Polymer
conditioning of sludges can also be used to enhance dewatering. The
ow water content of the highpressure filter presses can significantly
Waste Treatment Methods
18?
ower disposal costs (Groves and Bartman, 199la and 1991b; Mayer
and Cregar, 1991; Steward, 1991).
The effectiveness of mechanical methods to dewater solids from a
reserves pit and a production pit varies ( Wojtanowicz et al., 1987).
The dewatering of most oilfield wastes can be improved by precon
ditioning before mechanical separation with nonionic or lowcharge
anionic polymers with high molecular weights. Belt presses and
centrifuges show similar performance, but belt presses are difficult to
clean. Vacuum filtration and screw presses are not as effective because
of their low volume reduction of the solid waste stream. Comparison
of the effectiveness of several mechanical separations methods for
reserves and production pits are provided in Tables 63 and 64,
respectively. For these tables, initial solids contents of 10 wt% and
30.5 wt% were used, respectively.
Table 6-3
Effectiveness of Solids Separation Methods for Reserve Pits
Volume Reduction (vol%)
Solids Recovery (wt%)
Cake Dryness (wt% solids)
Effluent Solids (mg/1)
Belt Press
Centrifuge
Vacuum Filter
70
99.91
45
150
71
99.85
44
180
45
99.84
23
130
Source: after Wojtanowicz et al., 1987.
Copyright SPE, with permission.
Table 6-4
Effectiveness of Solids Separation Methods for Production Pits
Volume Reduction (vol%)
Solids Recovery (wt%)
Cake Dryness (wt% solids)
Effluent Solids (mg/1)
Source: after Wojtanowicz et al., J987.
Copyright SPE, with permission
Belt Press
Centrifuge
Screw Press
50
99.83
55
300
38
99.99
59
30
26
99.98
45
95
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Environmental Control in Petroleum Engineering
6.2.2
Removal of Hydrocarbons
A variety of methods are available to remove hydrocarbons from
solids, such as drill cuttings, contaminated soil, and produced sand.
These methods include washing, adsorption, filtration, heating, solvent
extraction, incineration, and biological degradation (U.S. Environ
mental Protection Agency, 1990). These methods are described below.
The effectiveness of these methods varies significantly. Pyrolysis
can reduce most hydrocarbon concentrations on solids to nondetectable
evels, while solvent extraction and distillation can reduce concen
ration to a few tens of mg/kg. Hydrocarbon concentrations following
simple filtration can be in the hundreds of mg/kg range (American
Petroleum Institute, 1987).
Washing
One of the least expensive ways to remove most of the hydro
carbons from solids is to wash them. The solids can be entrained in a
fluidized bed of upwardflowing, highvelocity water. This stream
agitates the solids and opens the pore system to release the oil. The
efficiency of this process can be enhanced by adding a surfactant
(soap) to the water to lower the interfacial tension holding the oil to
he solids. Washing is more effective in sandy soils containing low
amounts of clay.
A related process is to slurry the solids in a lowtoxicity base oil.
Although this process does not necessarily result in a lower hydrocar
bon concentration in the solids, it can replace the original hydrocarbon,
e.g., diesel, with a less toxic one.
If the volume of solids is small, they can be placed in an ultra
sound bath for cleaning. The highfrequency acoustic pulses in the bath
help release the hydrocarbons from the solids. Ultrasound baths work
well for laboratory scale operations, but are not appropriate for
oilfieldscale applications.
Adsorption
Another relatively lowcost method of removing some of the hydro
carbons contaminating solids is to mix the soil with a material that is
strongly oilwet, like coal or activated carbon (Ignasiak et al., 1990).
Waste Treatment Methods
189
A suspension of contaminated soil and the carbon can be tumbled in
water at elevated temperatures to allow the oil to be absorbed by the
carbon. The oily carbon is then separated from the water and clean
sand by flotation. The oily carbon can then be burned in conventional
coalfired power plants or buried in an approved facility.
Heating
Heating cuttings contaminated with hydrocarbons can help separate
the hydrocarbons from the solids, particularly when being washed in
water (Henriquez, 1990). This procedure is similar to using heat to
break emulsions and separate hydrocarbons and water.
Heating can also be used for hydrocarbon sludges (Hahn, 1993).
In this process, the sludges are heated above the boiling point of water
and allowed to flash to vapor. This separates the water and light
hydrocarbons from the heavier hydrocarbons. The high temperature
also lowers the viscosity of the heavy hydrocarbons, facilitating their
separation as a slurry.
Distiliation/Pyrolysis
A more expensive method for removing light and intermediate
weight hydrocarbon compounds is to distill them from the solids in a
retort furnace. The solid/hydrocarbon mixture is heated to vaporize the
light and medium molecular weight hydrocarbons and water. The gases
are removed from the hightemperature chamber by either a nitrogen
or steam sweep. After the vapors are subsequently cooled and con–
densed, the oil is separated from the water. The oil can be reused and
the solids and water sent to an appropriate disposal facility. To maxi
mize the separation of liquids and solids, the heating can be done in
a rotating drum with hammers to crush the solids while rotating.
Several commercial thermal distillation processes are available (Ruddy
et al, 1990).
Distillation systems, however, have several significant operations
imitations. Hydrocarbon vapors at high temperatures are a fire hazard,
corrosion problems increase significantly at high temperatures, and air
pollutants are emitted. The chemical structure of some hydrocarbons
s altered at high temperatures, making their reuse in some applica
ions, like drilling muds, impossible. If heavy hydrocarbon components
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Environmental Control in Petroleum Engineering
are present, they will not be distilled and will form a heavy residual tar
on the solids. For example, distillation may remove only about 65% of
he heavy polynuclear aromatics. Another limitation to distillation is the
high energy costs of heating the materials to a sufficiently high tempera
ure. An operating temperature of about 800°F may be required for
effective distillation of heavy ends (Young et al, 199la). An operating
emperature of 473°F, however, has proven to be effective in lowering
he hydrocarbon level of cuttings to 10 g/kg (Van Elsen and Smits, 1991),
If the distillation temperatures are high enough, the hydrocarbon
molecules will be broken by pyrolysis, forming coke. This would
solidify the remaining hydrocarbons, preventing their migration upon
disposal of the waste.
Incineration
Another way to remove hydrocarbons from solids is to burn the
mixture in an incinerator. Incinerators are specially designed burners
hat can burn the relatively small volume of combustible materials
ound in oily solids. Following combustion, the resulting ash, including
any salts and heavy metals, is solidified to prevent leaching of any
hazardous residue. Incineration typically removes over 99% of the
hydrocarbons in the soil.
A significant limitation to incinerators is that they emit air pollu
ants, particularly metal compounds like barium, cadmium, chromium,
copper, lead, mercury, nickel, vanadium, and zinc. Incineration des
roys hydrocarbon wastes, but merely changes the chemical form of
heavy metal wastes. Because of the air pollutants emitted, all incinera
tors require permits. Another limitation to incineration is that a second
ary fuel is required because the heat content of the hydrocarbons in
many petroleum solid wastes is insufficient for combustion, particu
larly when a high volume of noncombustible material is present, e.g.,
he solids. The need for secondary fuel increases the cost of operations.
Although incineration is expensive, it has low future liability (Goodwin
and Turner, 1990).
Solvent Extraction
Solvent processes can also be used to separate hydrocarbons from
solids. In these processes, a solvent with a low boiling point is mixed
Waste Treatment Methods
191
with the oily solids to wash the oil from the solids and dilute what
remains trapped. The solvent is then separated from the hydrocarbons
and solids by lowtemperature distillation and reused. Solvent extrac
tion is routinely used in the petroleum industry for extracting fluids
from cores during core analysis. Like distillation, solvent extraction
is expensive. Solvent extraction is more effective in sandy soils
containing little clay. Several commercial solvent extraction processes
are available (Ruddy et al., 1990).
A more exotic solvent extraction process uses critical or super–
critical fluids. In this process, the cuttings are placed in a pressure
chamber with a fluid near its critical point. Commonly used fluids
include carbon dioxide, propane, ethane, and butane. The pressure
is increased until the fluid passes above its critical point and becomes
a liquid. The liquid is then used as a solvent to wash the oil
from the solids. After the liquid mixture is separated from the
solids, the pressure is lowered. With the lower pressure, the super
critical fluid reverts to a gaseous state, leaving the extracted hydro–
carbons behind. The gas is then recycled. The process is expensive,
but eliminates many of the problems associated with hightemperature
thermal processes.
Biological Processes
Most hydrocarbons encountered in the upstream petroleum industry
can be biologically converted to carbon dioxide and water by microbes
like bacteria and fungi. During biological degradation, the hydro
carbons are eaten as food by the bacteria. This biological degrada
tion can be enhanced by providing the optimum conditions for mic
robe growth. The deliberate enhancement of biological degradation is
called bioremediation.
The effectiveness and speed of bioremediation in degrading hydro
carbons depends on a variety of environmental conditions, includ
ing temperature, salinity, pH, hydrocarbon type, heavy metal concentra
tion, soil texture, moisture content, and hydrocarbon concentration.
Because of this, the chemical composition of the hydrocarbon, the type
and level of background microorganisms, and the nutrient level at
the site must be determined and the environmental conditions con
trolled for optimum degradation (American Petroleum Institute, 1986b;
Hildebrandt and Wilson, 1991).
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Environmental Control in Petroleum Engineering
Naturally occurring bacteria can effectively degrade naturally occur
ing hydrocarbons, such as crude oil. In most cases, the appropriate
bacteria are already present in the environment and their populations
can be increased just by adding nutrients. In some cases, naturally
occurring bacteria have been artificially cultured and then released in
greater numbers to accelerate biodegradation of the hydrocarbons, but
he effectiveness of this augmentation is uncertain. Genetically engi
neered bacteria may be necessary to degrade some refined hydro
carbons, such as chlorinated solvents.
The most significant limitation for many bioremediation applications
s a lack of nutrients for bacterial growth. These nutrients, e.g.,
nitrogen, phosphorus, and some trace elements, can be added by way
of fertilizer. The amount and composition of fertilizer needed for
optimum degradation depends on what hydrocarbon is being degraded
and the bacteria being enhanced.
Oxygen is also needed for bioremediation to convert the hydro
carbons to carbon dioxide and water. Anaerobic biological degradation
without oxygen) also occurs, but is much slower and less efficient
han aerobic degradation. Oxygen is normally provided by ensuring
hat the pore system within the solids is sufficiently open for air to
low through it. One way to enhance the pore system is by adding
nert bulking agents like wood chips, bark, sawdust, tires, and shredded
vegetation to increase the mixture porosity. The use of inert bulking
agents is called composting bioremediation.
In most cases, water is also needed because it is the medium in which
he bacteria live. Bacterial growth normally occurs at water/hydrocarbon
nterfaces. For optimum degradation, the water content of the solids must
be balanced. If not enough water is present, bacterial growth will be
nhibited. If too much water is present, the access of oxygen and nutrients
o the bacteria will be limited, again inhibiting bacterial growth.
In some cases, surfactants have been added to the nutrient mixture
o solubilize and emulsify lowsolubility hydrocarbons, including
heavy aromatics and PAHs. Surfactants can also mobilize sorbed
microbial cells and contaminants from the soil surface to provide
greater access to microbial attack.
The degradation rate of hydrocarbons depends on the structure of
he hydrocarbon molecule and the type of bacteria involved. Paraffins
are the most susceptible to microbial attack, followed by isoparaffins
and aromatics. The polycyclic aromatic hydrocarbons (PAHs) are the
Waste Treatment Methods
193
most difficult to biodegrade. The speed of bioremediation is often mea
sured in terms of halflives of the hydrocarbon, i.e., the time for half of
the hydrocarbon to be biologically degraded. Typical degradation halflives
range from a few days for lowmolecularweight compounds to a number
of years for complex compounds (American Petroleum Institute, 1984).
When the oil has been degraded and hydrocarbon levels have been
reduced, the bacterial populations return to their initial level.
Specific bioremediation halflives have been reported as over 48
weeks for bunker C fuel (Song et al., 1990), 3757 weeks for crude
oil sludge (Loehr et al., 1992), less than 30 days for some normal
alkanes and aromatics (Loehr et al., 1992), five weeks for a Saudi
Arabian crude oil (Whiteside, 1993), eight weeks for crude oil under
optimum conditions (McMillen et al., 1993), and more than two years
for crude oil under nonoptimized conditions (McMillen et al., 1993.
Bioremediation with composting has also been successfully applied
with remediation times of five weeks for sludges and dieselcontami
nated soils (Martinson et al., 1993).
There are a number of difficulties, however, with applying bioreme
diation at hydrocarboncontaminated sites. The presence of dissolved
solids, such as heavy metals or salt in reserves pits, will inhibit
bacterial growth. Bioremediation projects can emit significant levels
of air pollutants. For example, the emission rates of benzene and
naphthalene may be high enough to require that respirators be worn
by workers (Myers and Barnhart, 1990). Such air emissions are
expected to limit the availability of permits for bioremediation projects
in the future. Finally, some bioremediation facilities have required
large amounts of water, which can be a problem in arid areas,
Filtration
If the hydrocarbon content of the solids is high, some of the free
hydrocarbons can be separated from the solids by mechanical filtration.
Filtration, however, is not effective for reducing hydrocarbon concen
trations to low levels.
6.2.3
Solidification
One way to treat contaminated solids is to solidify the mixture so
that the contaminants become part of the solid. Solidification reduces
194
Environmental Control in Petroleum Engineering
pollutant mobility and improves handling characteristics. Two types
of solidification have been used: adding materials to absorb free liquids
and adding materials to chemically bind and encapsulate the contami
nants. Most offsite disposal sites use solidification to treat the wastes
or final disposal by burial (Jones, 1990; Roberts and Johnson, 1990),
Absorbants are typically used to dewater reserves pits in areas where
he evaporation rate is low. Materials that have been added to the pits
o absorb free water include straw, dirt, fly ash, clays, kiln dust, fly
ash, and polymers.
The best solidification methods, however, are those that chemically
bind the contaminants. These methods are based primarily on portland
cement, calcium silicate, or aluminosilicate reactions (Carter, 1989;
Nahm et al., 1993). These materials, unlike fly ash or kiln dust, can
reduce the leachability of toxic heavy metals, asbestos, oils, and salts.
The mobility of metals from such solidification can be reduced by 80
90%, while that of organics can be reduced by 6099% (U.S. Environ
mental Protection Agency, 1990).
Vitrification by heating the solids to a high enough temperature to
melt silica has also been proposed (Buelt and Farnsworth, 1991), but
s likely to be too expensive for applications in the petroleum industry.
6.3 TREATMENT OF AIR EMISSIONS
During drilling and production activities, a substantial volume of
air pollutants can be generated and emitted. These pollutants include
hydrocarbons, sulfur oxides, nitrogen oxides, and particulates. A
variety of treatment methods are available, but their effectiveness
varies considerably with the pollutant being treated.
6.3.1
Hydrocarbons
The primary source of hydrocarbon emissions is from the exhaust
of internal combustion engines. Unfortunately, there is little that can
be done to treat these emissions other than to operate the engines
within their design specifications.
The vapor space in production tanks can collect volatile hydro
carbon vapors. These vapors can be collected and treated with vapor
ecovery systems (Webb, 1993). Casing gas from thermal enhanced
oil recovery operations may also contain high levels of hydrocarbon
Waste Treatment Methods
195
vapors. These casing gases can be collected in a separate gathering
system and treated by adsorption (Peavy and Braun, 1991).
Another source of hydrocarbon emissions are the fugitive emissions
arising from leaking valves and fittings. Because these emissions are
generally too spread out to be collected, their release must be pre
vented by replacing and repairing the leaking equipment.
Emissions from remediation projects of hydrocarboncontaminated
sites can contain volatile hydrocarbons. These hydrocarbons can be
collected by passing the emissions through a bed of activated carbon
or adsorptive polymer. Alternatively, the vapors can be bubbled through
water, where the hydrocarbons become dissolved. Although the dis
solution process can be effective in lowering hydrocarbon air emis
sions, the subsequently contaminated water must then be treated and
disposed. For some projects, catalytic oxidation may be used as a low
temperature alternative to incineration of volatile hydrocarbons.
6.3.2
Sulfur Oxides
Sulfur oxides are generated from the combustion of fuels containing
sulfur. Although these emissions can be treated to remove the sulfur,
the emission of sulfur can also be reduced or eliminated by the use
of lowsulfur fuel. A variety of scrubber systems are available to
remove sulfur from air emissions (Goodley, 1979).
6.3.3 Nitrogen Oxides
Nitrogen oxides are generated from hightemperature combustion
and from the combustion of fuels containing nitrogen (crude oil).
Unfortunately, these emissions are difficult to treat and may require
specially designed equipment.
Equipment to minimize the emission of nitrogen oxide in combus
tion gases includes low NOx burners, flue gas recirculators, selective
catalytic reduction devices, and selective noncatalytic systems. The
amount of nitrogen oxides emitted can also be lowered by reducing
the amount of oxygen in the combustion process. Unfortunately,
lowering oxygen in the combustion process increases the amount of
partially burned hydrocarbons created.
The impact of nitrogen oxides from fixed installations, such as
natural gas compressor stations, can be minimized by the stack height,
196
Environmental Control in Petroleum Engineering
ocation, and orientation with respect to other structures (Ramsey and
Roger, 1991).
63.4
Participates
Many combustion operations emit partially burned hydrocarbon
particulates from incomplete combustion. These particulates, such as
soot, can be removed by passing the flue gas through a scrubber, where
he particulates become entrained in the water.
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CHAPTER 7
Waste Disposal
Methods
The upstream petroleum industry generates a significant volume of
wastes, primarily produced water and drill cuttings. No matter how
effective a waste management plan or waste treatment program may
be, wastes will remain that must be disposed of. In some cases, the
final disposal can be onsite, while in other cases, the wastes must be
shipped for disposal offsite.
Ultimately, petroleum industry wastes can be disposed of above or
below the surface of either land or water. The suitability of these
disposal locations varies with the wastes being disposed.
7.1
SURFACE DISPOSAL
The easiest and least expensive method of waste disposal is to
discharge the wastes onto the ground or into surface waterways.
Although this has historically been a common disposal method for
many wastes, its use and misuse has been a major factor in the
increase in environmental regulations governing the petroleum industry.
Nevertheless, various forms of surface disposal are still appropriate
for many treated wastes.
7.1.1
Disposal of Water
Wastewater can be discharged directly into local streams, rivers, or
the ocean as long as its quality meets regulatory standards, i.e., its
concentration of suspended and dissolved solids, chemicals, and
hydrocarbons is sufficiently low. Surface discharge is regulated in most
areas, however, and permits for such discharge are required.
203
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When wastewater is discharged offshore, the water is typically
treated to remove only the hydrocarbons. Although the dissolved solids
(salt) concentrations of most produced waters are high enough to be
toxic to even marine life, the rapid mixing and dilution of the dis
charged water makes the resulting environmental impact negligible.
For nearshore discharges in shallow water, there is less opportunity
for mixing and dilution of the discharged water, and a toxic plume
can exist for some distance away from the discharge point. Such toxic
plumes are of particular concern when discharging a dense, highsaline,
oxygendeficient brine because it can be trapped in subsurface topo
graphic low areas. Because this trapped brine can significantly impact
the local marine life, permits to discharge highsalinity brines near the
shore may be difficult to obtain, even if the hydrocarbon content is low.
When wastewater is discharged into onshore freshwater locations, both
the hydrocarbon and dissolved solids concentrations must be low. Because
of the high cost of removing dissolved solids, surface discharge of
wastewater is generally possible only if the initial dissolved solids
concentration of the water is low. Surface discharge into dry stream beds
is a common way to dispose of treated water in arid areas like Wyoming.
Surface discharge into percolation ponds is also used in some areas.
In percolation ponds, the water is allowed to percolate into the under
saturated (vadose) zone, where it eventually evaporates back into the
atmosphere. Because of the lack of control over where the water goes,
this disposal method is being phased out. Discharge into evaporation
ponds is also an option in many arid areas, particularly if a liner is
used to prevent leaching of dissolved solids.
7.1.2 Disposal of Solids
Waste solids can be discharged directly onto the ground or into the
ocean as long as their quality meets regulatory standards, i.e., the
concentration of contaminants like hydrocarbons and heavy metals is
sufficiently low. Because such discharges are regulated, permits are
required in most areas.
Offshore Discharges
Offshore discharges of treated solids, such as drill cuttings and
produced solids, are permitted in some areas. Offshore discharges,
Waste Disposal Methods
205
however, are prohibited within three miles of shore in the United
States, and the discharge of oilbased drilling mud wastes are pro
hibited in all United States waters. Where offshore discharges are
prohibited, waste solids must be transported to shore for disposal
(Arnhus and Slora, 1991). This is generally more expensive than
offshore treating and discharge.
Onshore Discharges
Many solid wastes, particularly drill cuttings and produced solids,
can be discharged by spreading them over the land surface. If the
solids have been treated and are not contaminated with hydrocarbons,
salt, or heavy metals, then obtaining permits for surface disposal may
be relatively simple.
The suitability of a solid waste for surface discharge can be assessed
through its electrical conductivity (EC), sodium adsorption ratio
(SAR), the exchangeable sodium percentage (ESP), and the oil and
grease (O&G) levels. Maximum • values generally recommended
for these parameters are: EC < 4 mmhos/cm, SAR < 12, ESP < 15%,
and O&G < 1% (Deuel, 1990). These parameters are discussed in
more detail in Chapter 3. Another measure of the suitability of a solid
waste for surface discharge is its heavy metal content. Maximum
recommended accumulations of heavy metals in soil are presented in
Table 7–1.
Treated waste solids can be used for road and site construction.
Construction grade gravel and sand can be used as fill material on
roads and drilling pads. Such use of treated solids minimizes the need
for quarried gravel, which further lowers the environmental impact of
drilling and production activities (Schumacher et al., 1990).
Land treatment can be used for the disposal of solids containing
only hydrocarbons, particularly if the treatment is designed to degrade
the hydrocarbons by biological processes (Bleckmann et al., 1989;
Biederbeck, 1990). There are two major forms of land treatment in
use: landspreading and landfarming. Landspreading is when wastes
are spread over the surface of the ground and then tilled into the soil.
After this initial tilling, no further action is usually taken. Landfarrning
is an enhanced version of landspreading in which additional processing
of the soil is conducted after the initial tilling. In landfarming, the soil
is commonly processed for several years after the initial application
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Table 7-1
Maximum Recommended Heavy
Metal Concentration in Soii
Element
Arsenic
Boron
Barium
Beryllium
Cadmium
Cobalt
Chromium
Copper
Mercury
Manganese
Molybdenum
Nickel
Lead
Selenium
Vanadium
Zinc
Soil Concentration (mg/kg)
300
3*
**
50
3
200
1,000
250
10
1,000
5
100
1,000
5
500
500
*Concentration in soil-paste extract.
**Depending on site conditions, can be as high as 100,000 mg/kg.
Source: Anderson et al., 1983.
Copyright Butterworth-Heinemann Publishers, 1983, with permission.
of the waste solids. This additional processing may include adding
fertilizers and tilling repeatedly to increase oxygen uptake in the soil.
Most farmers do not object to landspreading because it provides
some irrigation, helps condition the soil, stabilizes wind erosion,
improves soil structure, and can improve crop yield (American Petrol
eum Institute, 1983; Deuel, 1990; Zimmerman and Robert, 1990).
There are two significant problems with land treatment that may
limit future applications. First, land treatment provides little control
over where mobile (leachable) fractions of the waste will go. Second,
the spreading of oily wastes results in emissions of volatile organic
compounds. These problems may result in a treatment project to be
in violation of some applicable laws and regulations governing air
pollution. This has led to land treatment being banned in some areas.
Waste Disposal Methods
207
Road spreading is another disposal method for hydrocarbon
contaminated solids. The wastes are mixed with other construction
materials and spread over gravel roads. The oil helps hold the road
materials together, making such wastes an effective dust suppressant.
Depending on the quality and type of solids, these wastes may also
be used in the construction of new road beds. Road spreading is
commonly used for the disposal of produced sand in Alberta and has
been tested in California. Not all wastes are suitable for road spread
ing, however. The waste must not contain significant amounts of salt
water, fracturing acids, other nonhydrocarbon contaminants, halo
genated hydrocarbons, or manufactured oils. The hydrocarbons must
be nonvolatile to minimize air pollution problems. Produced sand from
heavy oil operations are well suited for road spreading because of their
low content of aromatics and volatile hydrocarbons.
The environmental impact of road spreading is low for properly
prepared wastes. The metals content of most oily wastes can be lower
than that of asphalt, a common road paving material. Elevated levels
of chloride, metals, or hydrocarbons have not been observed in ditch
samples collected along roads used for the disposal of solid wastes
(Kennedy et al., 1990; Cornwell, 1993). Because most of the wastes
hat are candidates for road spreading are highvolume, lowtoxicity
solids, disposal by road spreading reduces the volume of wastes that
must be disposed of in overused landfills. Nevertheless, the lack of
control over the spread of wastes is expected to limit and may even
prohibit its future use.
7.2 SUBSURFACE DISPOSAL
Subsurface disposal is the most widely used method for the disposal
of most petroleum industry wastes. Liquids are usually injected into
deep subsurface formations through injection wells, and solids are
usually buried in shallow pits at a drill site. If wastes are considered
hazardous under applicable regulations, however, disposal at a licensed
hazardous waste disposal site may be required.
7.2.1
Disposal of Liquids
The most common disposal method for waste liquids, such as
produced water, is to inject them into a subsurface formation. Details
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Environmental Control in Petroleum Engineering
on planning, installation, operation, and maintenance of disposal wells
have been provided by the American Petroleum Institute (1978). The
cost of drilling and completing a disposal well can be a significant
expense in wastewater disposal.
Disposal wells must be completed in a formation that is permeable
and porous, and has a low pressure and a large storage volume. The
disposal formation must also be geologically isolated from any fresh
water aquifers. To prevent the water from plugging the formation, the
water must normally be treated to remove free and emulsified oil,
suspended solids, and some dissolved solids, such as iron and scale,
prior to disposal.
One disposal method that is growing in popularity is annular injec
tion in existing wells. In this process, the wastewater is injected down
the annulus of an existing injection or production well and into a
formation above the existing completion. A packer is used to isolate
the disposal zone from the existing injection or production zone. This
disposal method can eliminate the cost of drilling a separate disposal
well. The disposal zone must still meet all requirements for protecting
freshwater aquifers.
A major concern with underground disposal of water is the potential
for the well to provide a vertical communication path from the disposal
formation to any overlying freshwater aquifers. Possible communica
tion paths include flow up the inside of the casing through leaks in
the casing and flow up the outside of the casing through a bad cement
bond. The presence of leaks in the casing can be detected through
mechanical integrity tests. Unfortunately, there are no reliable ways
to detect the flow of water up the outside of the casing.
Mechanical integrity tests are required in the United States to
determine whether leaks are present in casing. These tests are con
ducted with tubing set in casing. Two types of tests are commonly
used (Kamath, 1989). In one type of test, the level of any liquid in
the annulus above the packer is monitored for changes. In most cases,
the fluid level will rise as fluid leaks from the higherpressured
disposal zone to the lowerpressured zones overlying it. In the second
type of test, the annulus is pressurized and its pressure is then moni
tored. If there is a leak, the pressure in the annulus will decline. The
annulus pressure method, however, requires that the well be isothermal
and that there are no interactions between the liquid and gas in the
annulus. Because these requirements are rarely present, the fluid level
Waste Disposal Methods
209
method is normally considered more reliable than the annulus pressure
method for detecting leaks in the casing.
Although there are no reliable methods to detect whether or not
water is flowing up the outside of casing, a number of methods are
available that can detect flow in some cases. These methods are
generally limited to large leaks or high fluid flow rates. Noise logs
can detect highvolume fluid movement behind casing, but are sensi
ive to extraneous sources of sound. Neutron activation logs can detect
water movement in some cases (Arnold and Paap, 1979; McKeon et
al., 1991; Uswak and Howes, 1992). Injecting a boron solution into
the well and logging with a pulsed neutron log to monitor boron
migration has been proposed (Bount et al., 1991). Radioactive tracers
can be injected into the well and the well logged with a gammaray
detector to test for tracer movement. Acoustic cement bond logs can
provide evidence of a bad cement bond in some cases.
The possibility of pressure communication between the disposal
zone and overlying formations can be tested by separately completing
an intermediate zone above the disposal zone and below the overlying
freshwater aquifer. If the pressure in the intermediate zone responds
o the injection pressure into the disposal zone, then a leak behind the
casing is indicated (Poimboeuf, 1990).
If a well fails a mechanical integrity test, the well normally must
be repaired before it can be used as an injection well. One method of
repairing a leak in casing is to install a concentric packer to isolate
he leak and allow fluid flow past the bad section of casing (Wilson,
1990). Other methods to repair wells that fail a mechanical integrity
test include squeeze cementing, running a liner, or plugging and
abandoning the well.
Failure of a mechanical integrity test does not necessarily mean that
freshwater aquifers will be contaminated; it only indicates the possi
bility of water flow up the annulus. No upflow will occur if the
disposal formation is underpressured, e.g., if its flow potential (abso
lute pressure minus hydrostatic gradient) is lower than that of the
overlying zones. It has been suggested that wells that fail a mechanical
ntegrity test and are underpressured could still be safely used without
repair if the fluid level in the annulus is continuously monitored to
ensure that no vertical flow of fluids occurrs (Janson and Wilson,
1990). The disposal of water by gravity feed, by which there are no
pumps to pressurize the disposal zone, has also been proposed for such
210
Environmental Control in Petroleum Engineering
wells (Meyer, 1990). Regulatory approval to use a well that fails a
mechanical integrity test may not be possible in some areas.
7.2.2
Disposal of Solids
Subsurface burial is a common method for disposal of solid wastes.
Drill cuttings and used mud are typically left in reserves pit after a
well is drilled. After the free liquids are removed, the remaining
materials are covered by soil and the site is revegetated. Such onsite
disposal is allowed in most areas, provided there are no hazardous
materials mixed with the waste.
One major concern with the burial of solids is the potential for
heavy metals, hydrocarbons, and salts to migrate away from the site,
Salt buried in reserves pits can migrate both downward and upward
(McFarland et al., 1990). The two metals most commonly found in
drilling muds at concentrations above those found in most soils are
barium and chromium. These metals, along with mercury, are in a
nonsoluble form and have a very limited potential for migration or
plant uptake (American Petroleum Institute, 1983). For pits containing
high salt or hydrocarbon levels, regulations may require the use of an
impermeable pit liner to prevent leaching. The leaching rate for unlined
pits could also be reduced by covering the buried waste with an
impermeable cap to prevent stormwater infiltration (Roberts and
Johnson, 1990).
In arctic regions, the disposal of drilling wastes in pits using below
grade freezeback has been proposed. In this process, the drilling wastes
are buried in a deep pit dug into the permafrost. After closure, the
materials will freeze, minimizing any migration of soluble components
from the site. Only waterbased muds, cuttings, and excess cement can
be successfully disposed of by this method; any freezedepressing
materials like brines, glycols, or alcohols may be prohibited (Maunder
et al., 1990). The longterm stability of these pits in the event of
climate changes, however, is not known (Fristoe, 1990).
A developing new technology for the disposal of drill cuttings is
to grind them into small particles and inject them into a well as a
slurry (Malachosky et al., 1991; Smith, 1991; Minton and Secoy,
1993). In most cases, annular injection is used for the slurry. If
fracturing is required for the slurry to be accepted by the formation,
it will be necessary to ensure that the disposal zone and any hydraulic
Waste Disposal Methods
211
fractures remain isolated from overlying freshwater aquifers (Andersen
et al., 1993). The design of slurry injection projects can be difficult,
however, because reliable data on the rheology and fracturing proper
ties of the slurry are limited (Crawford and Lescarboura, 1993).
If hazardous materials are present, regulations may require that the
wastes be shipped to a commercial offsite disposal facility. Materials
that normally cannot be disposed of by onsite burial include pipe dope
cans, waste lubricating oils, mud sacks, solvents, or excess treatment
chemicals. In most cases, commercial offsite disposal facilities consist
of an engineered landfill. If the landfill is permitted to accept hazard
ous wastes, it must have a synthetic liner with a leachate monitoring
and collection system. Other types of landfills, e.g., those with clay
liners and that have less stringent monitoring requirements, can accept
nonhazardous wastes. Waste disposal at commercial facilities should
be used with caution, however, because hazardous waste regula
tions in the United States can impose liability on all companies for
any wastes at the facility, regardless of who actually sent any particu
lar waste.
Naturally occurring radioactive materials (NORM) generated at
production sites must also be safely disposed of in ways to prevent
unnecessary human exposure to nuclear radiation. Several studies have
concluded that many disposal methods are available that are effective
in keeping human exposure to nuclear radiation from NORM well
below 100 mREM/year (American Petroleum Institute, 1990; Miller
and Bruce, 1990). These disposal methods included landspreading,
landspreading with dilution, shallow burial, disposal in plugged and
abandoned wells, and subsurface injection (with or without hydraulic
fracturing). Regulations governing the disposal of NORM are currently
being formulated. Until approved disposal options become available,
NORM contaminated equipment and soil should be stored onsite.
Abandoned offshore platforms must also be disposed of. The plat
form must be removed to eliminate any navigational hazards it poses.
In most instances, explosives are used for cutting the legs to free the
platform from the sea floor. Such explosive cutting has been identified
as a possible cause of deaths of endangered sea turtles and marine
animals (Arscott, 1989). Other methods of cutting platform legs have
been considered, including sawing with diamond wires, flame cutting
with acetylene and oxygen, arc cutting with steel electrodes, plasma
arc cutting with argon, cryogenic fragmentation, and highpressure
212
Environmental Control in Petroleum Engineering
water jet cutting . These methods, however, are significantly more
hazardous to the work crews involved (McNally, R., 1987; AlHassani,
1988; Pittrnan et al., 1961; Murrell and Faul, 1989).
Once the platform has been removed, it can be disposed of by
transporting it to land, cutting it into pieces, and burying it. This
process, however, is expensive. In some areas, abandoned platforms
can be sunk to the sea floor and used as artificial reefs to enhance
offshore fisheries. The platform provides a solid substrate for aquatic
plants to grow, which then attract fish. The "Rigs to Reefs" program
may be particularly attractive in offshore areas having few natural
reefs, such as the U.S. Gulf of Mexico. Such programs are currently
being developed in a number of states.
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American Petroleum Institute, "Summary and Analysis of API Onshore
Drilling Mud and Produced Water Environmental Studies," API Bulletin
D19, Washington, D.C., Nov. 1983.
American Petroleum Institute, "Management and Disposal Alternatives for
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Anderson, D.C., Smith, C., Jones, S. G., and Brown, K. W., "Fate of Con
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K. W. Brown, G. B. Evans, Jr., and B. D. Frentrup (editors), Wobern, MA:
Butterworth Publishers, 1983.
Andersen, E. E., Louviere, R. J., and Witt, D. E., "Guidelines for Designing
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Protection Agency's Exploration and Production Environmental Conference,
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IADC 21949 presented at the Society of Petroleum Engineers SPE/IADC
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Arnold, D. M. and Paap, H. J., "Quantitative Monitoring of Water Flow
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Arscott, R. L., "New Directions in Environmental Protection in Oil and Gas
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Biederbeck, V. O., "Using Oily Waste Sludge Disposal to Conserve and
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Sept. 10–13, 1990, pp. 10251038.
Bleckmann, C. A., Gawel, L. J., Whitfill, D. L., and Swindoll, C. M., "Land
Treatment of OilBased Drill Cuttings," paper SPE 18685 presented at the
1989 Society of Petroleum Engineers SPE/IADC Drilling Conference, New
Orleans, LA, Feb. 28–March 3, 1989.
Bount, C, G., Copoulos, A. E., Myers, G. D., "A Cement ChannelDetection
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Cornwell, J. R., "Road Mixing Sand Produced from SteamDrive Operations,"
paper SPE 25930 presented at the Society of Petroleum Engineers/Environmental
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San Antonio, TX, March 7–10, 1993.
Crawford, H. R. and Lescarboura, J. A., "Drill Cuttings Reinjection for
Heidrun: A Study," paper SPE 26382 presented at the Society of Petroleum
Engineers 68th Annual Technical Conference and Exhibition, Houston, TX,
Oct. 3–6, 1993.
Deuel, L. E., "Evaluation of Limiting Constituents Suggested for Land
Disposal of Exploration and Production Wastes," Proceedings of the U.S.
Environmental Protection Agency's First International Symposium on Oil
and Gas Exploration and Production Waste Management Practices, New
Orleans, LA, Sept. 10–13, 1990, pp. 411430.
Fristoe, B., "Drilling Wastes Management for Alaska's North Slope," Proceed
ings of the U.S. Environmental Protection Agency's First International
Symposium on Oil and Gas Exploration and Production Waste Management
Practices, New Orleans, LA, Sept. 10–13, 1990, pp. 281292.
anson, L. G., Jr. and Wilson, E. M., "Application of the Continuous Annular
Monitoring Concept to Prevent Groundwater Contamination by Class II
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First International Symposium on Oil and Gas Exploration and Produc
tion Waste Management Practices, New Orleans, LA, Sept. 1013, 1990,
pp. 7392.
Kamath, K. I., "Regulatory Control of Groundwater Contamination by
Hazardous Waste Disposal Wells: An Engineering Perspective," paper SPE
19744 presented at the Society of Petroleum Engineers 64th Annual
Technical Conference and Exhibition, San Antonio, TX, Oct. 8–11, 1989.
Kennedy, A, J., Holland, L. L., and Price, D. H., "Oil Waste Road Application
Practices at the Esso Resources Canada Ltd., Cold Lake Production
Project," Proceedings of the U.S. Environmental Protection Agency's First
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Environmental Control in Petroleum Engineering
International Symposium on Oil and Gas Exploration and Production Waste
Management Practices, New Orleans, LA, Sept. 1013, 1990, pp. 689702,
Malachosky, E., Shannon. B. E., and Jackson, J. E., "Offshore Disposal of
OilBased Drilling Fluid Waste; An Environmentally Acceptable Solution,"
paper SPE 23373 presented at the Society of Petroleum Engineers First
International Conference on Health, Safety, and Environment, The Hague,
Netherlands, Nov. 10–14, 1991.
Maunder, T. E., Le, K, M., and Miller, D. L., "Drilling Waste Disposal in
the Arctic Using BelowGrade Freezeback," paper SPE 20429 presented
at the Society of Petroleum Engineers 65th Annual Technical Conference
and Exhibition, New Orleans, LA, Sept. 2326, 1990.
McFarland, M., Ueckert, D. N., and Hartmann, S., "Evaluation of Selective
Placement Burial for Disposal of Drilling Fluids in West Texas," Proceed
ings of the U.S. Environmental Protection Agency's First International
Symposium on Oil and Gas Exploration and Production Waste Management
Practices, New Orleans, LA, Sept. 10–13, 1990, pp. 455–466.
McKeon, D.C., Scott, H. D., Olesen, J. R., Patton, G. L., and Mitchell R,
J., "Improved OxygenActivation Method for Determining Water Flow
Behind Casing," SPE Formation Evaluation, Sept. 1991, pp. 334–342.
McNally, R., "Variety of Factors Impact Platform Removal," Petroleum
Engineer International, April 1987.
Meyer, L., "Simple Injectivity Test and Monitoring Plan for Brine Disposal
Wells Operating by Gravity Flow," Proceedings of the U.S. Environmental
Protection Agency's First International Symposium on Oil and Gas Explor
ation and Production Waste Management Practices, New Orleans, LA.
Sept. 1013, 1990, pp. 865872.
Miller, H. T. and Bruce, E. D., "Pathway Exposure Analysis and the Identifi
cation of Waste Disposal Options for Petroleum Production Wastes Con
taining Naturally Occurring Radioactive Materials," Proceedings of the
U.S. Environmental Protection Agency's First International Symposium on
Oil and Gas Exploration and Production Waste Management Practices, New
Orleans, LA, Sept. 1013, 1990, pp. 731–744.
Minton, R. C. and Secoy, B., "Annular Reinjection of Drilling Wastes,"
J. Pet. Tech., Nov. 1993, pp. 1081–1085.
Murrell, D. and Faul, R., "Platform Removal with HighPressure Fluids
Environmentally Sound and Efficient," Proceedings of the PettoSafe "89
Conference, Houston, TX, Oct. 3–5, 1989.
Pittman, F. C., Harriman, D. W., and St. John, J. C., "Investigation of
AbrasiveLadenFluid Method for Perforation and Fracture Initiation,"
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Poimboeuf, W. W., "An Early Warning System to Prevent USDW Con
tamination. Environmental Underground Injection Equipment for Hazardous
Waste Disposal Methods
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and NonHazardous Liquid Waste Disposal. Injection Well and Monitoring
Well in the Same Borehole," Proceedings of the U.S. Environmental
Protection Agency's First International Symposium on Oil and Gas Explor
ation and Production Waste Management Practices, New Orleans, LA,
Sept. 1013, 1990, pp. 4372.
Roberts, L. and Johnson, G., "A Study of the Leachate Characteristics of
Salt Contaminated Drilling Wastes Treated with a Chemical Fixation/
Solidification Process," Proceedings of the U.S. Environmental Protec
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Sept. 10–13, 1990, pp. 933944.
Schumacher, J. P., Malachosky, E., Lantero, D. M., and Hampton, P. D,,
Minimization and Recycling of Drill Cuttings for the Alaskan North
Slope," paper SPE 20428 presented at the Society of Petroleum Engineers
65th Annual Technical Conference and Exhibition, New Orleans, LA,
Sept. 2325, 1990.
Smith, R. L, "The Cuttings Grinder," paper SPE 22092 presented at the
Society of Petroleum Engineers International Arctic Technical Symposium,
Anchorage, AK, May 29–31, 1991.
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Using a Transient Oxygen Activation Technique," Journal of Canadian
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Wilson, E. M., '"The Application of Concentric Packers to Achieve Mech
anical Integrity for Class II Wells in Osage County, Oklahoma," Proceed
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Zimmerman, P. K., and Robert, J. D., "Landfarming Oil Based Drill Cutt
ings," Proceedings of the U.S. Environmental Protection Agency's First
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Management Practices, New Orleans, LA, Sept. 1013, 1990, pp. 565576.
CHAPTER 8
Remediation of
Contaminated Sites
Many petroleum industry sites have been contaminated from previous
activities or can become contaminated through accidental releases of
various materials. In many cases, remediation will be required to
estore the impacted area. Sites that may require remediation include
old reserves pits, onshore release sites of hydrocarbons or contami
nated water, and places where oil slicks from offshore releases are
blown onshore.
Unfortunately, the complex pore structure and fluid transport path
ways of soil can make remediation difficult. Hydrocarbons can be
ound in various places in soil. Most are trapped by capillary pressure
as a discrete liquid phase within the pores of the soil. If a sufficient
volume of hydrocarbons has been released, it can exist in a separate,
mobile phase that floats on top of the groundwater. Hydrocarbons can
also be dissolved into the groundwater and be transported away from
he release site. Volatile hydrocarbons can be found as a vapor in air
aturated pores. Dissolved solids can also be found in various places
n soil. They can remain dissolved and migrate with groundwater or
hey can be absorbed onto the soil solids.
Because of the complex distribution of contaminants in soil, a compre
hensive site evaluation may be required before the optimum remediation
process can be selected and properly implemented. A number of site
emediation methods are available and are reviewed below.
8.1
SITE ASSESSMENT
An important process in the cleanup of contaminated sites is to
assess their potential to impact human health and the environment
216
Remediation of Contaminated Sites
217
before remediation begins. A site assessment is the first step in
determining what remediation method is to be used, if any.
Site assessments are normally conducted in stages (American Petrol
eum Institute, 1989). The first stage is to gather all relevant back
ground information about the site. This includes reviewing available
records and reports and may include interviewing site personnel. From
his information, the magnitude and composition of the release is
estimated. The next stage is to characterize the site. The purpose of
site characterization is to determine the exact locations, contaminant
concentrations, and extent of the contaminated zone and to evaluate
he potential for the contaminants to migrate from the site. Depending
on the magnitude of the release and its potential for adverse environ
mental impact, a risk assessment study may be needed. A risk assess
ment study would quantify the potential environmental impact of the
various remediation processes being considered, and the results could
be used when negotiating the specific details of a site remediation
project with applicable regulatory agencies.
An important part of site assessment is to develop a detailed
sampling and sample analysis plan that clearly identifies the objectives
of the analysis and how those objectives are to be met. This plan must
also address quality assurance and control to ensure that the data
obtained accurately reflect the actual concentrations being measured
(Keith et al., 1983). This plan determines the number of samples to
be obtained and their locations. Normally, a network of sampling
points is selected around the site. Geological and hydrological factors
must be considered in selecting each point, including any local ground
water flow, the hydraulic conductivity (permeability) of the soil,
geological heterogeneities that can affect fluid flow, and geochemical
processes, such as ion exchange, that can cause contamination to
migrate at a rate different from the physical flow of groundwater.
Additional sampling sites may be added if a statistical analysis of the
nitial samples indicates that the confidence limits are unacceptably
ow (Wojtanowicz et al., 1989).
Two types of samples are generally obtained: core samples and fluid
samples. Core samples provide information about liquids trapped with
he solids by capillary pressure, while fluid samples provide informa
ion about mobile liquids. The type of samples required depends on
he type of contaminant and may be specified by applicable regulatory
agencies. Other types of measurements, such as electromagnetic
218
Environmental Control in Petroleum Engineering
surveys to characterize the extent of brine plumes, can also be used
(Young, 1991; Dalton, 1993). A detailed discussion of sampling and
analysis is given by Johnson and James (1989).
Sampling procedures must be designed to provide unbiased data
throughout the cleanup process (American Petroleum Institute, 1983 and
1985a). Procedures that can contaminate samples include how the sampling
device is emplaced at the site. Drilling can alter the in situ geochemical
environment by flushing with drilling fluid or by allowing the commingl
ing of fluids in different zones. The presence of foreign materials like
grout or bentonite around the wellbore can contaminate water flowing into
the well. To flush such contaminants from the well, typically eight to ten
well volumes of water are pumped from the well before samples are taken.
Samples can also become contaminated from exposure to atmospheric
pollutants, particularly oxygen. The composition of obtained samples can
be altered by degassing or by sitting stagnant for a few weeks before
testing, allowing bacteria to grow. Finally, human error in any of the stages
of obtaining the sample can result in sample contamination.
For groundwater remediation projects that are expected to take a
number of years to complete, the timing of sampling during remediation
should be systematic, not random. Systematic sampling is easier to
schedule and administer and will allow seasonal variations to be identified
and accounted for. For many cleanup projects, sampling four to six times per
year may be adequate to ensure that the cleanup dynamics are observed
and to minimize expensive redundancy (Johnson and Jennings, 1990).
Once obtained, the samples must then be accurately analyzed, A
variety of analytical procedures are available for different contaminants
(National Research Council, 1985; American Petroleum Institute, 1985g
and 1987a). For compounds with concentrations in the partsper
million or higher range, the accuracies of most analytical procedures
are generally good. For trace contaminants, however, consistent results
may be difficult to obtain. Different measurement methods can also
yield different results, particularly if improper extraction methods are
used (Holliday and Deuel, 1993). Sophisticated analytical techniques
like gas chromatography may be required for accurate results. Regulatory
agencies may specify the types of analyses that must be conducted.
After the data have been obtained, a statistical analysis of the data
must be conducted. The type of statistical analysis conducted will
depend on the needs of the study and how the resulting conclu
sions will be used. A variety of statistical tools are available through
ime series and trend analysis. When analyzing data, however, it is
Remediation of Contaminated Sites
219
important to include all of the data in the analysis. Using the lowest
measured concentrations and discarding the highest may be illegal.
The difficulty in obtaining reliable data for the composition of
contaminated sites was dramatically demonstrated through independent
studies conducted by the U.S. Environmental Protection Agency and
the American Petroleum Institute (Holliday and Deuel, 1990). In these
studies, the same reserves pits, produced water pits, and production
facilities were independently sampled and analyzed by the two agen
cies. As seen in Table 81, no correlation was found between the
Table 8-1
Correlation of Independent Measurements of Waste Composition
Constituent
Sodium
Potassium
Calcium
Magnesium
Sum of cations
Chlorides
Electrical conductivity
Sodium absorption ratio
Total suspended solids
Arsenic
Boron
Barium
Chromium
Copper
Lead
Nickel
Zinc
Oil and grease
Total organic carbon
Napthalene
Toluene
Ethylbenzene
PH
Moisture content
Pit Liquids
Pit Solids
Produced Water
Good
Good
Good
Good
Good
Poor
—
—
None
None
Poor
None
—
Poor
None
Good
None
—
None
—
Good
Good
Good
Good
Good
Good
None
Good
None
None
Good
Good
—
—
__
___
—
Good
None
None
None
—
Good
—
Source: after Holliday and Deuel, 1990.
Copyright SPE, with permission.
—
—
None
None
Good
Poor
Good
None
None
Poor
None
Poor
None
None
None
None
None
—
___
—
—
Poor
Good
None
Good
None
None
—
220
Environmental Control in Petroleum Engineering
concentrations obtained by the two agencies for many important waste
constituents. Further, the correlation was not improved by sending
samples to different laboratories. Unfortunately, insufficient data were
obtained to determine the exact cause of the poor correlation.
An important step in any cleanup program is to determine when
cleanup is complete. This includes determining the acceptable level
of residual contaminants. Acceptable levels are typically determined
by comparing the contaminant levels to the standards for "clean" water
or to levels that existed prior to the release. These levels are normally
sitespecific and are determined by negotiation with the appropriate
regulatory agencies (Cooper and Hanson, 1990). Determining cleanup
levels may require risk assessment studies to be conducted.
Because of the statistical variability in any data and possible prob
lems with sampling and analysis, identifying when a particular stand
ard has been achieved can be difficult. Remediation to where the
applicable standard is met with a 90% confidence limit is often used,
although the actual level required is normally determined through
negotiation with applicable regulatory agencies on a casebycase basis
(Hoffman, 1993).
In determining whether further remediation is required, political and
institutional pressures that have no relevance to protecting human
health or the environment often exist. Too often these pressures are
not based on accurate scientific information and can result in additional
remediation costs with little benefit to the environment. This problem
is further compounded by the disagreement on what scientific stand
ards should be used. Even the relatively simple question of whether
cleanup should be based on the level of total petroleum hydrocarbons
or the levels of individual hydrocarbon compounds has not been
resolved. In some cases, the actual risk to the environment often
depends more on the composition of a contaminant than on its total
amount, particularly when only trace quantities are present. The
importance of accurate scientific information is evidenced in the
conflicting stories about the environmental impact related to the Exxon
Valdez spill (Maki et al., 1993).
8.2
REMEDIATION PROCESSES
A number of remediation processes are available to clean up con
taminated sites (Sims, 1990). Some are suitable for cleaning up
Remediation of Contaminated Sites
221
contaminated Soil or subsurface groundwater, while others are suitable
for cleaning up contaminated shorelines. These processes vary signifi
cantly in how completely they remove the contaminants, in the time
they require, and in their associated costs. Successful cleanup may
require a combination of remediation processes (Peters and Wentz,
1991), Cleanup of offshore oil releases is discussed in Appendix D.
Because most remediation processes entail their own environmental
hazards, care must be taken in selecting which method to use. The
potential impact will depend on the remediation process used and the
type of habitat being cleaned. Shoreline habitats are particularly
sensitive to remediation processes (American Petroleum Institute,
1985d and 1985e).
One of the concerns that must be addressed when designing reme
diation projects is to prevent any further spread of the contaminant
plume. Containment of the plume is of particular concern if remedia
tion is expected to take a number of years, as it may for contaminated
groundwater. Containment can be accomplished by placing physical
or hydraulic barriers around it. Physical barriers consist of an imperme
able material that is emplaced around the contaminant plume to
prevent its migration. Grout can be injected into the soil, where it
solidifies to form an impermeable barrier. Sheet piling made of steel
plates can be driven into the ground around the contaminant. Trenches
can be dug and backfilled with an impermeable medium to form a
slurry wall. Hydraulic barriers consist of a set of wells around the site
from which fluid is withdrawn at a rate at least equal to the ground
water flow rate. The withdrawal point becomes a low point for the
hydraulic pressure, inducing all groundwater in the immediate area,
including the contaminant plume, to flow to the wells instead of away
from the site,
Natural Processes
For some contaminated sites, the best remediation process may be
to do nothing and let natural processes degrade and remove any
contaminants. This option may be particularly suitable for oil spills
in sensitive shoreline habitats, where implementing a remediation
process may cause more damage than leaving the spilled oil (Kiesling
et al,, 1988). Natural processes that remove hydrocarbons include
evaporation, photooxidation, and bacterial action, coupled with dispersion
222
Environmental Control in Petroleum Engineering
from wind and wave action. Natural processes can be enhanced by
manually removing free oil with absorbants.
Pump and Treat
Traditionally, the most common way to remediate hydrocarbon
contaminated groundwater is to pump the groundwater from onsite
wells or trenches and then treat the water. Pumping creates a fluid cone
or water depression around the well that establishes a hydraulic
gradient to drive fluid to the well faster than the normal groundwater
flow rate. Because of this, pump and treat normally produces large
volumes of water. The produced water must be treated to remove the
hydrocarbons before being discharged. Treated water can then be
reinjected for disposal or to help drive remaining contaminants to the
pumping wells. Treatment methods for hydrocarboncontaminated
water are discussed in Chapter 6.
One proposed method to minimize the volume of water produced
is to install pumps with oilwet elements that only allow entry of
hydrocarbons. These pumps, however, do not establish the water
depression around the wellbore, limiting the flow rate of hydrocarbons
to the well. The use of horizontal wells to improve hydrocarbon
capture has also been proposed (Karisson, 1993).
Because of capillary trapping of hydrocarbons in the pore spaces,
pump and treat will not completely recover all of the hydrocarbons
at a spill site. These trapped hydrocarbons may be water soluble and
can dissolve into the groundwater as it flows past. Thus, trapped
hydrocarbons can provide a source of groundwater contamination long
after all free hydrocarbons have been removed. Because of this,
additional remediation may be required.
Soil Flushing
One way to speed the removal of hydrocarbons from soil is to flush
water through the spill site. If additives are used with the water, many
of the trapped hydrocarbons can also be removed. The environmental
impacts of any additives used, however, must be low.
Surfactants and other chemicals can be added to the water to
enhance the removal of trapped hydrocarbons in soil. These materials
lower the capillary pressure between the hydrocarbons and groundwater,
Remediation of Contaminated Sites
223
allowing the hydrocarbons to migrate through the pore structure to the
wells, where they can be removed. Chemicals can also increase the
solubility of some hydrocarbon compounds in water. This increased
solubility can accelerate the removal of trapped hydrocarbons by
continued flushing. Laboratory studies of gasoline recovery using
surfactants have been successful (American Petroleum Institute, 1985f
and 1986g).
Flushing can also enhance remediation of hydrocarboncontaminated
shorelines. For example, small barriers and channels can be constructed
to enhance natural flushing in tidal flats or river deltas to remove oil
from stagnant areas. Oil on rocky beaches can be hosed off by jets of
water or steam. Highpressure or hightemperature jets can be more
effective in removing the hydrocarbons, but can result in more damage
to the habitat.
Vaporization
Volatile hydrocarbons can be removed from soil by vaporization.
Natural vaporization can be enhanced by tilling the soil. For hydro
carbons located deeper than normal tilling depths, vaporization can be
enhanced by injecting air or by pulling a vacuum on the soil. Air
injection has proven effective in removing gasoline in both laboratory
and field studies (American Petroleum Institute, 1985b and 1986b).
This process lowers the partial pressure of the hydrocarbon in the
vapor phase in the soil, inducing further vaporization. Air injection is
generally more effective at hydrocarbon removal, although vacuum
extraction requires less air to be handled.
An emerging variation on volatilization is to heat the soil. Because
the vapor pressure of volatile hydrocarbons increases almost exponen
tially with temperature, volatilization can be significantly enhanced
through heating. Injecting steam has proven to be effective in vaporiza
tion of volatile hydrocarbons (Hunt et al., 1988; Udell and Stewart,
1990). Heating through radio frequency or electrical currents has also
been proposed.
Volatilization may not be a good remediation process if the hydro
carbon contaminant contains nonvolatile components. Once the vola
tile components have been removed, the remaining components will
be heavier, more viscous, and less likely to be recovered by any
subsequent processes. However, because the most toxic hydrocarbon
224
Environmental Control in Petroleum Engineering
components tend to be the most volatile, any remaining hydrocarbons
n the soil would tend to have a relatively low toxicity. Because
volatilization releases materials that may contribute to air pollution.
permits may be required.
Bioremediation
Biological degradation can be used at some sites to remove hydrocar
bons in soil. Fertile soil naturally contains up to one million hydrocarbon
degrading bacteria per gram of dry soil (Testa and Winegardner, 1991),
By adding nutrients and ensuring the availability of oxygen, in situ
bioremediation can effectively degrade many hydrocarbon contami
nants. This process can take several months to several years to complete,
however, and is difficult to control (U.S. Environmental Protection
Agency, 1990; American Petroleum Institute, 1986a and 1986h).
One factor controlling the effectiveness of in situ bioremediation
s the soil structure. Sandy soils with a high permeability allow higher
evels of biological activity than do soils containing significant quanti
ies of silt or clay. The more permeable soils permit a more rapid transport
of air (oxygen), water, and nutrients to the sites of biological activity.
The availability of oxygen is another factor controlling the effective
ness of in situ bioremediation. To help ensure an adequate supply of
oxygen, air is commonly injected into the formation in a process called
air sparging. The injection of hydrogen peroxide has also been suggested
as a means of increasing the oxygen levels, but its effectiveness has
not been established (American Petroleum Institute, 1985c and 1986c).
Hydrogen peroxide, however, is toxic and its use may not be permitted.
In situ bioremediation may not be allowed in some areas. Some
egulatory agencies prohibit the injection of chemicals into ground
water, preventing the addition of nutrients needed for bacterial growth.
Excavation
For small sites, all of the contaminated soil can be excavated. The
excavated soil can then be treated by one of the methods discussed
n Chapter 6. The primary benefit of excavation is the insurance that
all of the contaminant has been removed, which lowers the potential
or any future liability costs. The primary disadvantage of excavation,
however, is its high cost. Excavation and disposal at an offsite
Remediation of Contaminated Sites
225
hazardous waste disposal facility may be the only economically viable
cleanup option for sites contaminated with heavy metals like chromium
(Campbell and Akers, 1990).
Brine Contamination
The most common remediation process for brinecontaminated soil
is to flush the soil with fresh water to leach the salt away. In many
areas, natural processes like flooding and rainwater provide sufficient
fresh water to remove the salt. If natural processes are inadequate,
remediation can be enhanced through irrigation.
Because soil is a strong cation exchange medium, particularly when
it has a high clay content, remediation by leaching can be a very slow
process. Leaching can be enhanced through the addition of a cationic
solution of calcium, such as gypsum (calcium sulfate) or calcium
nitrate. Calcium, which has a lower impact on plant growth than
sodium, replaces sodium in the exchange sites in the clays, allowing
sodium to be leached away more rapidly. Field tests have shown that
applying a calcium solution has been successful in revegetating some
brinecontaminated soils. If the soil already contains a high concentra
tion of sulfate ions, as in the case of a reserves pit site with barium
sulfate (barite), the solubility of gypsum can be lowered, rendering it
less effective for remediation (Hartmann et al., 1990; American Petrol
eum Institute, 1983).
For soils marginally contaminated with brine, one simple remedia
tion process is to increase the soil's fertility. An increase in fertility
may allow plants to be grown in the contaminated soil. Native grass
mulch or aged manure can be disked into the top foot of soil, followed
by leaching with water. This will provide additional fertilizer, as well
as opening the pore structure for improved water and air transport.
These sites can also be revegetated with salttolerant plants (Ueckert
et al., 1990).
Sulfur Contamination
At some production sites, sulfur has been removed from sour natural
gas and then stored at the site. At many sites, molten sulfur has been
deposited on the soil to create a base pad upon which additional sulfur
has been piled.
226
Environmental Control in Petroleum Engineering
The first step in cleaning these sites generally consists of excavating
he pad. The excavated sulfur is then broken into pieces to remove
rocks, logs, and other such materials. Separation from the remaining
soil can be achieved by either melting the sulfur or through a froth
flotation process. In froth flotation, pieces of soil and sulfur are
agitated in water to break them up. The mixture is then aerated, and
he lighter sulfur particles attach to the air bubbles and float to the
top where they are separated from the solids (Adamache, 1990).
The contaminated soil around the pad can be neutralized by adding
calcium carbonate (limestone) to the soil. The soil structure, organic
carbon content, and nutrient levels may also need to be restored.
Reclamation of these sites may take five to seven years (Leggett and
England, 1990).
Adamache, I., "Contaminated Sulphur Recovery by Froth Flotation," Proceed
ings of the First International Symposium on Oil and Gas Exploration and
Production Waste Management Practices, New Orleans, LA, Sept. 3013,
1990, pp. 185198.
American Petroleum Institute, "Groundwater Monitoring and Sample Bias,"
API Publication 4367, June 1983.
American Petroleum Institute, "Field Evaluation of Well Flushing Proce
dures," API Publication 4405, June 1985a.
American Petroleum Institute, "Subsurface Venting of Hydrocarbon Vapors
from an Underground Aquifer," API Publication 4410, Sept. 1985b.
American Petroleum Institute, "Feasibility Studies on the Use of Hydrogen
Peroxide to Enhance Microbial Degradation of Gasoline," API Publication
4389, May 1985c.
American Petroleum Institute, "Oil Spill Response: Options for Minimizing
Adverse Ecological Impacts," API Publication 4398, Aug. 1985d.
American Petroleum Institute, "Oil Spill Cleanup: Options for Minimizing
Adverse Ecological Impacts," API Publication 4435, Dec. 1985e.
American Petroleum Institute, "Test Results of Surfactant Enhanced Gasoline
Recovery in a LargeScale Model Aquifer," API Publication 4390, April
19851
American Petroleum Institute, "Detection of Hydrocarbons in Groundwater
by Analysis of Shallow Soil Gas/Vapor," API Publication 4394, 1985g.
American Petroleum Institute, "Field Application of Subsurface Biodegra
dation of Gasoline in a Sand Formation," API Publication 4430, 1986a.
Remediation of Contaminated Sites
22?
American Petroleum Institute, "Forced Venting to Remove Gasoline Vapor
from a LargeScale Model Aquifer," API Publication 4431, I986b.
American Petroleum Institute, "Enhancing the Microbial Degradation of
Underground Gasoline by Increasing Available Oxygen," API Publication
4428, 1986c.
American Petroleum Institute, "Underground Movement of Gasoline on
Groundwater and Enhanced Recovery by Surfactants," API Publication
4317, I986g.
American Petroleum Institute, "Beneficial Stimulation of Bacterial Activity
in Ground Waters Containing Petroleum Products," API Publication 4427,
1986h.
American Petroleum Institute, "Manual of Sampling and Analytical Methods
for Petroleum Hydrocarbons in Groundwater and Soil," API Publication
4449, 1987a.
American Petroleum Institute, "A Guide to the Assessment and Remediation
of Underground Petroleum Releases," API Publication 1628, August 1989.
Campbell, R. E. and Akers, R. T, "Characterization and Cleanup of Chromium
Contaminated Soil for Compliance with CERCLA at the Naval Petroleum
Reserve No. 1 (Elk Hills): A Case Study," paper SPE 20714 presented at
the 65th Annual Technical Conference and Exhibition, New Orleans, LA,
Sept. 2326, 1990.
Cooper, D. E. and Hanson, J. B., "Establishing Site Specific Cleanup Stan
dards at Superfund Sites," proceedings of How Clean is Clean? Cleanup
Criteria for Contaminated Soil and Groundwater, Air and Waste Manage
ment Association, Boston, MA, Nov. 79, 1990.
Dalton, M. S., "The Use of Geophysical Surveys for Conductive Groundwater
Plume Assessment During Remediation," paper SPE 25984 presented at
the SPE/EPA Exploration and Production Environmental Conference, San
Antonio, TX, March 710, 1993.
Hartmain, S., Ueckert, D. N., and McFarland, M. L., "Evaluation of Leaching
and Gypsum for Enhancing Reclamation and Revegetation of Oil Well
Reserve Pits in a Semiarid Area," Proceedings of the First International
Symposium on Oil and Gas Exploration and Production Waste Management
Practices, New Orleans, LA, Sept. 1013, 1990, pp. 431441.
Hoffman, J., "A Survey of Regulatory Approaches to Cleanup Standards for
Soil Contaminated by Spills of Crude Oil or Salt Water," paper SPE 25985
presented at the SPE/EPA Exploration and Production Environmental
Conference, San Antonio, TX, March 710, 1993.
Holliday, G. H. and Deuel, L. E., "A Statistical Review of API and EPA
Sampling and Analysis of Oil and Gas Field Wastes," paper SPE 20711
presented at the 65th Annual Technical Conference and Exhibition, New
Orleans, LA, Sept. 2325, 1990.
228
Environmental Control in Petroleum Engineering
Holliday, G. H. and Deuel, L. E., "Determining Total Petroleum Hydro
carbons in Soil," paper SPE 26394 presented at the 68th Annual Technical
Conference and Exhibition, Houston, TX, Oct. 36, 1993.
Hunt, J. R., Sitar, N., and Udell, K. S., "Nonaqueous Phase Liquid Transport
and Cleanup: 1. Analysis of Mechanisms," Water Resources Research, Vol.
24, No. 8, Aug. 1988, pp. 12471258.
Johnson, L. D. and James, R. H., "Sampling and Analysis of Hazardous
Wastes," in Standard Handbook of Hazardous Waste Treatment and Disposal
H. M. Freeman (editor), New York: McGrawHill Book Company, 1989.
Johnson, W. SB. and Jennings, K. V. B., "Evaluating the Effectiveness of
Corrective Actions Involving Ground water," paper SPE 20062 presented
at the 60th California Regional Meeting, Ventura, CA, April 46, 1990.
Karisson, H., "Horizontal Systems Technology for ShallowSite Remedia
tion," J. Pet, Tech., Feb. 1993, pp. 160165.
Keith, L. H., Crummett, W., Degan, J., Libby, R. A., Taylor, J. K., and
Wentler, G., "Principles of Environmental Analysis," Analytical Chemistry,
Vol. 55, No. 14, Dec. 1983, pp. 22102218.
Kiesling, R. W., Alexander, S. K., and Webb, J. W., "Evaluation of Alternative
Oil Spill Cleanup Techniques in a Spartina alterniflora Salt Marsh,"
Environmental Pollution, Vol. 55, No. 1, 1988, pp. 221238,
Leggett, S. A., and England, S. L., "Sulphur Block Basepad Reclamation
Programs Undertaken at Three Facilities in Central Alberta," Proceedings
of the First International Symposium on Oil and Gas Exploration and
Production Waste Management Practices, New Orleans, LA, Sept. 1013,
1990, pp. 945954.
Maki, A. W., Burns, W. A., and Bence, T. E., "Management of Environmental
Impact Studies: A Perspective on the Exxon Valdez Environmental Assess
ment," paper SPE 26677 presented at the 68th Annual Technical Con–
ference and Exhibition, Houston, TX, Oct. 36, 1993.
National Research Council, Oil in the Sea: Inputs, Fates, and Effects,
Washington, D.C.: National Academy Press, 1985.
Peters, R. W. and Wentz, C. A., "Remediation of Oil Field Wastes," Advances
in Filtration and Separation Technology, Vol. 3, Pollution Control Technology for Oil and Gas Drilling and Production Operations, American
Filtration Society. Houston: Gulf Publishing Co., 1991, pp. 5866.
Sims, R. C., "Soil Remediation Techniques at Uncontrolled Hazardous Waste
Sites: A Critical Review," Journal of the Air and Waste Management
Association Reprint Series: RS15, 1990.
Testa, S. M., and Winegardner, D. L., Restoration of Petroleum-Contaminated
Aquifers. Chelsea, Michigan: Lewis Publishers, Inc., 1991.
Udell, K. S. and Stewart, L. D., "Combined Steam Injection and Vacuum
Extraction for Aquifer Cleanup," presented at the Conference of the
Remediation of Contaminated Sites
229
International Association of Hydrogeologists, Calgary, Alberta, April 18
20, 1990.
Ueckert, D. N., Hartmann, S., and McFarland, M. L., "Evaluation of Con
tainerized Shrub Seedlings for Bioremediation of Oilwell Reserves Pits,"
Proceedings of the First International Symposium on Oil and Gas Explora
tion and Production Waste Management Practices, New Orleans, LA,
Sept. 1013, 1990, pp. 403410.
U. S. Environmental Protection Agency, "International Evaluation of In Situ
Biorestoration of Contaminated Soil and Groundwater," EPA 54090012,
Sept. 1990.
Wojtanowicz, A. K., Field, S. D., Krilov, Z., and Spencer, F. L., "Statistical
Assessment and Sampling of DrillingFluid Reserve Pits," SPE Drilling
Engineering, June 1989, pp. 162170.
Young, G. N., "Guidelines for the Application of Geophysics to Onshore E&P
Environmental Studies," paper SPE 23369 presented at the First Inter
national Conference on Health, Safety, and Environment, The Hague,
Netherlands, Nov. 1014, 1991.
APPENDIX A
Environmental
Regulations
Past environmental practices by segments of the petroleum industry
have lead to the loss of public confidence that the industry is able to
regulate itself and still protect the environment. Because of this, a large
number of environmentallyrelated laws have been passed, and more
are under consideration.
Regulations vary significantly from country to country, state to state,
and locality to locality. In most areas, there are multiple, overlapping
regulatory agencies that govern various aspects of oil and gas explora
tion and production. Because these regulations are rapidly changing,
any summary of them can be quickly outdated.
Many environmental regulations impose both civil and criminal
penalties, with fines and jail terms for violators. Civil penalties can
be imposed on both companies and individuals for violations, regard
less of intent. Criminal penalties can be imposed on individuals for
deliberate violations of the regulations. It is the individual's responsi
bility to ensure that their actions are in compliance with all existing
regulations. The courts in the United States have generally held that
supervisors and managers "know" what their employees are doing and
thus can be held liable for their employees' actions.
Most environmental laws in the United States are based on the
concept of strict liability. Strict liability means that neither negligence
nor wrongful intent are necessary for liability to be imposed. The
company or person that violated the law will be held responsible, no
matter what mitigating circumstances may be present, including sabo
tage or natural disaster.
Good communications between industry, legislators, and regulatory
agencies are needed in developing meaningful regulations. Input from
230
Environmental Regulations
231
ndustry is important to ensure that new regulations are based on
accurate scientific information and that they contribute to real environ
mental protection without adding a useless burden to industry.
This appendix gives a brief overview of many of the laws and
egulations impacting drilling and production activities. More extensive
summaries are available (Gilliland, 1993; U.S. Department of Energy,
1991). Regulatory agencies should be contacted prior to initiating any
drilling and production activity, however, to ensure that those activities
will be conducted in compliance with whatever the current regulations
at that time and place may be.
UNITED STATES FEDERAL REGULATIONS
A number of federal environmental regulations affect the upstream
petroleum industry. These regulations are complex and require con
siderable knowledge and effort to ensure compliance. The major
egulations are briefly summarized Table A1 and are discussed below.
Additional regulations may also apply that impact drilling and produc
ion activities.
Environmental regulations are generally broad and can overlap. In
some cases, they can be inconsistent. For example, drilling muds are
exempt from the Resource Conservation and Recovery Act (RCRA),
Subtitle C, and can be legally disposed of in reserves pits. Reserves
pit contents such as drilling muds, however, are not exempt from the
Comprehensive Environmental Response, Compensation, and Liability
Act (Superfund).
Although the U.S. Environmental Protection Agency is responsible
or promulgating these regulations, individual states can be granted
primacy if they adopt regulations that are at least as strict as the
ederal regulations. Most oil and gas producing states have received
primacy and these regulations are enforced at the state level.
Resource Conservation and Recovery Act (RCRA)
The Resource Conservation and Recovery Act (RCRA) was initially
enacted in 1976 and amended in 1980 to establish a system for
managing hazardous solid wastes. This act specifies criteria for determin
ng whether wastes are hazardous or nonhazardous and promulgated
equirements on how each are to be managed. Hazardous wastes are
232
Environmental Control in Petroleum Engineering
Table A-1
Overview of Federal Environmental Regulations
Resource Conservation and
Recovery Act (RCRA)
Regulates management, treatment,
and disposal of hazardous wastes,
Safe Drinking Water Act
Regulates injection wells that may
contaminate freshwater aquifers.
Clean Water Act
Regulates activities that may
pollute surface waters.
Comprehensive Environmental
Response, Compensation, and
Liability Act (CERCLA)
Regulates cleanup of existing
hazardous waste sites.
Superfund Amendments and
Reauthorization Act (SARA)
Regulates reporting of storage and
use of hazardous chemicals.
Clean Air Act
Regulates activities that emit air
pollutants.
Oil Pollution Act
Regulates emergency response
plans for oil discharges.
Toxic Substances Control Act
Regulates testing of new
chemicals.
Endangered Species Act
Regulates actions that jeopardize
endangered or threatened species.
Hazard Communication Standard
Regulates the availability of
information on chemical hazards to
employees.
National Environmental Policy Act
NEPA)
Regulates actions of federal
government that may result in
environmental impacts.
egulated under Subtitle C and nonhazardous wastes are regulated
under Subtitle D. The regulations for hazardous wastes are consider
ably more stringent than those of nonhazardous wastes. As discussed
below, most but not all wastes generated during drilling and production
of oil are exempt from RCRA: Subtitle C.
Environmental Regulations
233
Under RCRA, a waste is any material that is discarded or is intended
o be discarded. It is the intent of future use that determines whether
t is considered a waste regulated under RCRA. This act also defines
solid wastes as any wastes that are either solid, semisolid, liquid, or
gases contained in storage vessels. It further defines a hazardous waste
as any solid waste that can cause or significantly contribute to an
ncrease in mortality or in serious irreversible or incapacitating rever
sible illness, or pose a substantial present or potential hazard to human
health or the environment when improperly treated, stored, transported,
disposed of, or otherwise managed.
Under RCRA, it is a crime to
1, knowingly cause hazardous materials to be transported to an
unpermitted facility or to knowingly transport hazardous mate
rials without a manifest,
2, knowingly treat, store, or dispose of hazardous wastes without
a permit or in violation of a permit,
3. knowingly falsify records, labels, manifests, or other documents
used for complying with the Act,
4. or knowingly fail to comply with, or interfere with, recordkeeping
requirements under the Act.
Violations of RCRA include fines of up to $50,000 per day and two
years of imprisonment. If human life is threatened by "knowing
endangerment," violations are a crime with fines of up to $1,000,000
and 15 years of imprisonment.
The EPA has established five criteria to determine whether a waste
s hazardous or not under this act. There are four generic criteria that
are based on the waste properties. These criteria are discussed below.
The fifth criterion is for the waste to be listed by name. Listed wastes
are those that are known to be hazardous, such as carcinogens and
poisons. The designation of whether a material is considered hazardous
or not is normally provided on Material Safety Data Sheets.
A waste is considered to be characteristically hazardous if it fits
any of the following generic criteria:
• Ignitability. A waste is considered ignitable if it presents a fire
hazard during routine management. A waste is considered ignit–
able if it is a liquid and has a flash point less than 140°F; if it is
not a liquid and is capable of causing fire through friction,
absorption of moisture, or spontaneous chemical changes and,
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Environmental Control in Petroleum Engineering
when ignited, burns so vigorously that it creates a hazard; or if it is
an ignitable compressed gas or an oxidizer as defined under U.S.
Department of Transportation regulations. Examples of ignitable
wastes include acetone, isopropanol, hexane, and methanol.
• Corrosivity. A waste is considered corrosive if it is able to
deteriorate standard containers, damage human tissue, and/or
dissolve toxic components of other wastes. An aqueous waste is
considered corrosive if it has a pH less than or equal to 2 or
greater than or equal to 12.5. A nonaqueous liquid is corrosive
if it corrodes SAE 1020 steel at a rate greater than 0.25 inches
per year at a temperature of 130°F. Although there is no provision
for corrosivity of solids, many states require that a sample be
placed in distilled water and the resulting pH be measured.
Examples of corrosive wastes include sodium hydroxide, potas
sium hydroxide, and acids.
• Reactivity. A waste is considered reactive if it has a tendency to
become chemically unstable under normal management conditions
or react violently when exposed to air or mixed with water, or if
it can generate toxic gases. Specific regulatory definitions for
reactivity have not been developed. Examples of reactive wastes
include cyanide or sulfide solutions, waterreactive metals, and
picric acid.
• Toxicity. A waste is considered toxic if it can leach toxic com
ponents in excess of specified regulatory levels upon contact with
water. A list of materials and the level above which they would
be considered toxic under RCRA is shown in Table A2. The
test procedure to be used, called toxicity characteristic leaching
procedure (TCLP), is carefully specified under the regulations and
is very expensive to conduct. A summary of the TCLP procedure as
it applies to the petroleum industry has been prepared by the Ameri
can Petroleum Institute (American Petroleum Institute, 1990a).
If a waste is considered to be hazardous under RCRA, "cradleto
grave" management and tracking of the waste is then required, includ
ng waste generation, transportation, treatment, storage, and disposal.
The generator of the waste can be held liable for the waste, no matter
who it has been passed on to or how long ago the waste was disposed.
After an extensive review of wastes generated by the upstream
petroleum industry, it was determined that those wastes were not
Environmental Regulations
Table A-2
Regulatory Limits for Toxicity Criterion Under RCRA
Contaminant
Arsenic
Barium
Benzene
Cadmium
Carbon tetrachloride
Chlordane
ChJorobenzene
Chloroform
Chromium
oCresol
mCresol
pCresol
Cresol
2,4D
1,4Dichlorobenzene
1,2Dichloroethane
1,1Dichloroethylene
2,4Dinitrotoluene
Endrin
Heptachlor
Hexachlorobenzene
Hexachloro1,3butadiene
Hexaehloroethane
Lead
Lindane
Mercury
Methoxychlor
Methyl ethyl ketone
Nitrobenzene
Pentachlorophenol
Pyridine
Selenium
Silver
Tetrachloroethylene
Toxaphene
Trichoroethylene
2,4,5Trichlorophenol
2,4,6Trichlorophenol
2,4,5TP (Silvex)
Vinyl chloride
Regulatory Level (mg/L)
5.0
100.0
0.5
1.0
0.5
0.03
100.0
6.0
5.0
200.0
200.0
200.0
200.0
10.0
7.5
0.5
0.7
0.13
0.02
0.008
0.13
0.5
3.0
5.0
0.4
0.2
10.0
200.0
2.0
100.0
5.0
1.0
0.7
0.7
0.5
0.5
400.0
2.0
1.0
0.2
235
23S
Environmental Control in Petroleum Engineering
intrinsically hazardous (U.S. Environmental Protection Agency, 1987;
American Petroleum Institute, 1983). Because of this, most of these
wastes have been exempted from RCRA: Subtitle C. This exemption
includes drilling muds, produced water, and other wastes directly
associated with drilling and production activities. This exemption gives
operators the ability to manage most drilling and production wastes
as nonhazardous wastes, although waste management must still be In
compliance with the many other existing regulations.
Not all wastes generated during drilling and production are exempt
from RCRA. Nonexempt wastes include those that are generated from
the maintenance of equipment or that are not unique to exploration
and production activities. Furthermore, some exempt wastes can lose
their exemption upon custody transfer, e.g., crude oil loses its exemp
tion when it reaches a refinery. Wastes that are sent to certain offsite
disposal facilities that are not dedicated to petroleum wastes may also
lose their exemption.
A list of RCRA: Subtitle C exempt wastes and a list of RCRA
nonexernpt wastes are provided in this appendix. A simple rule of
thumb can be used to help determine whether a waste is exempt or
not. If the waste originated from a well, was introduced into a well,
or carne into contact with the production stream during removal of
produced water or other contaminants from the production stream, the
waste is probably exempt.
In addition to the RCRA designation of hazardous wastes, states can
also generate their own lists of hazardous and nonhazardous materials.
Local regulatory agencies should be consulted for current lists.
Nonexempt wastes are not necessarily hazardous and do not neces
sarily require management under RCRA: Subtitle C. They are hazard
ous only if they meet one of the previously mentioned hazardous
criteria. If there is reason to believe that a nonexernpt waste may
exhibit one of the hazardous waste characteristics (toxic, corrosive,
ignitable, or reactive), it should be tested to determine whether or not
it is hazardous or not.
Mixing of exempt and nonexernpt wastes should be avoided, if possible,
because the mixture may become nonexempt. The following guidelines
can be used to indicate whether or not the mixture would be exempt:
1. Mixing of a nonhazardous waste (exempt or nonexempt) with
an exempt waste results in a mixture that is also exempt.
Environmental Regulations
23?
RCRA: Subtitle C Exempt Wastes
Produced Water.
Drilling Fluids,
Drill Cuttings.
Rig wash.
Drilling fluids and cuttings from offshore operations disposed of onshore.
Well completion, treatment, and stimulation fluids.
Basic sediment and water and other tank bottoms from storage facilities
that hold product and exempt waste.
Accumulated materials like hydrocarbons, solids, sand, and emulsions
from production separators, fluid treating vessels, and production
impoundments.
Pit sludges and contaminated bottoms from storage or disposal of exempt
wastes,
Workover wastes.
Gas plant dehydration wastes, including glycolbased compounds, glycol
filters, filter media, backwash, and molecular sieves.
Gas plant sweetening wastes for sulfur removal, including amine, amine
filters, amine filter media, backwash, precipitated amine sludge, iron
sponge, hydrogen sulfide, scrubber liquids and sludges.
Cooling tower blowdown.
Spent filters, filter media, and backwash (assuming the filter itself is not
hazardous and the residue in it is from an exempt waste stream).
Packing fluids.
Produced sand.
Pipe scale, hydrocarbon solids, hydrates, and other deposits removed from
piping and equipment prior to transportation. Scale formed in boilers is
nonexempt, however.
Hydrocarbonbearing soil.
Pigging wastes from gathering lines.
(continued on next page)
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Environmental Control in Petroleum Engineering
RCRA: Subtitle C Exempt Wastes
(continued)
Wastes from subsurface gas storage and retrieval, except for the listed
nonexempt wastes.
Constituents removed from produced water before it is injected or
otherwise disposed of.
Liquid hydrocarbons removed from the production stream but not from oil
refining.
Gases removed from the production stream, such as hydrogen sulfide and
carbon dioxide, and volatilized hydrocarbons.
Materials ejected from a producing well during the process known as
blowdown.
Waste crude from primary field operations and production.
Light organics volatilized from exempt wastes in reserves pits or
impoundments or production equipment.
Geothermal production fluids.
Hydrogen sulfide abatement wastes from geothermal energy production.
2, Mixing of a characteristically hazardous nonexempt waste with
an exempt waste creates a nonexempt hazardous waste if the
mixture exhibits the same hazardous characteristic (ignitability,
corrosivity, reactivity, or toxicity) as the initial hazardous waste.
If the mixture does not exhibit the same hazardous characteristic,
the waste is exempt, even if it exhibits a different hazardous
characteristic. Testing is required to determine whether the
mixture is characteristically hazardous. Mixing of a charac
teristically hazardous waste with a nonhazardous or exempt waste
for the purpose of dilution to make the waste nonhazardous is
considered a treatment process and is subject to RCRA: Subtitle
C hazardous waste regulations and permitting requirements.
3. Mixing of a listed hazardous waste with a nonhazardous exempt
waste results in a hazardous nonexempt waste, regardless of the
proportions used in the mixture.
Environmental Regulations
239
RCRA Nonexempt Wastes
Unused fracturing fluids or acids.
Gas plant cooling tower cleaning wastes.
Painting wastes.
Oil and gas service company wastes, such as empty drums, drum rinsate,
vacuum truck rinsate, sandblast media, painting wastes, spent solvents,
spilled chemicals, and waste acids.
Vacuum truck and drum rinsate from trucks and drums transporting or
containing nonexempt waste.
Refinery wastes.
Liquid and solid wastes generated by crude oil and tank bottom
reclaimers.
Used equipment lubrication oils.
Waste compressor oil, filters, and blowdown.
Used hydraulic fluids.
Waste solvents.
Waste in transportation pipelinerelated pits.
Caustic or acid cleaners.
Boiler cleaning wastes.
Boiler refractory bricks.
Boiler scrubber fluids, sludges, and ash.
ncinerator ash.
Laboratory wastes.
Sanitary wastes.
Pesticide wastes.
Radioactive tracer wastes.
Drums, insulation, and miscellaneous solids.
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Environmental Control in Petroleum Engineering
Even though most drilling and production wastes are exempt, many
of the wastes would actually test hazardous by the RCRA criteria
(McHugh et al., 1993). The hazardous criteria most commonly respon
sible for failed tests for ignitability and toxicity, e.g., the benzene
concentration of produced water.
Safe Drinking Water Act
The Safe Drinking Water Act was passed in 1974 to protect under
ground sources of drinking water (USDW) from contamination. USDWs
are freshwater aquifers that contain fewer than 10,000 mg/1 total
dissolved solids or that supply water for human consumption or for
any public water system, do not contain minerals or hydrocarbons that
are commercially producible, and are situated at a depth or location
which makes the recovery of water for drinking economically or
technologically practical.
The Safe Drinking Water Act regulates underground injection wells
through the Underground Injection Control (UIC) program. This
program established five classes of injection wells for different types
of wastes:
» Class I: Hazardous waste disposal wells and disposal wells for
industrial and municipal wastes meeting certain criteria.
• Class II: Wells for injecting oilfield fluids, whether for enhanced
recovery operations or for disposal and for injecting hydrocarbon
liquids into underground storage chambers.
• Class III: Wells used for extracting minerals like sulfur, solution
mining of minerals, in situ gasification of oil shale and coal, or
recovery of geochemical energy to produce electricity.
• Class IV: Wells used to dispose of hazardous and radioactive
wastes which meet certain criteria.
« Class V: Injection wells that do not fall into any of the other four
criteria.
Virtually all of the fluids injected into the ground during drilling
and production activities use Class II wells. Fluids approved for
injection into Class II wells include fluids produced from oil and gas
wells, commingled waste waters from gas plants (if nonhazardous at
the time of injection), and fluids injected for enhanced or improved
oil recovery operations.
Environmental Regulations
241
To ensure protection of USDWs, all Class II injection wells require
a permit prior to drilling. They must be completed in a zone that is
solated from overlying strata by one or more layers of impermeable
zones. The wells must be constructed with quality materials (tubulars
and cement) and follow methods to ensure their integrity (the ability
o confine fluids to the desired zone). They must be tested every five
years for mechanical integrity to verify that they do not provide a flow
channel between the injection zone and overlying strata.
Class II wells normally are operated at injection pressures below
he fracture pressure of the formation to ensure that vertical fractures
are not created that can provide a channel through the impermeable
zones to other layers. If it can be shown that any fractures will not
extend to USDWs, a permit may be obtained.
A major concern with the operation of Class II injection wells is
he presence of nearby wells that may provide a communication path
between the (injection) disposal formation and USDWs. When waste
water is injected, the target formation is pressurized. This pressure can
drive contaminated water up nearby wells to USDWs. To prevent this
from occurring, Class II wells are subject to an "area of review"
(AOR) requirement. This requirement states that no wells can exist,
within a given area of the Class II well, that are not properly com
pleted or plugged. Normally, this AOR is one quarter of an acre. The
AOR requirement may mandate new casing and cement for nearby
wells, plugging and abandonment of other wells, and possibly, replug
ging of previously abandoned wells. If the AOR requirement is not
met, a permit for a Class II well may not be granted. If a problem
AOR well is located on an adjacent lease, that well must also be fixed
before a permit can be obtained.
Clean Water Act
The Federal Water Pollution Control Act Amendments (Clean Water
Act) were passed in 1972 to protect surface waters by preventing or
minimizing discharges of materials like oil, produced water, or drilling
mud. It was amended in 1987 to focus more strongly on toxic dis
charges and nonpoint source pollution.
Under this act, the discharge of oil onto surface waters in harmful
evels is prohibited without a permit. Surface waters include marine
environments, lakes, rivers, ponds, streams, and dry drainage channels
242
Environmental Control in Petroleum Engineering
hat have the potential to flow water. Harmful levels include those that
cause a sheen or discoloration on the surface of the water or a sludge
or emulsion that can be deposited beneath the water. This act also
regulates the discharge of stormwater flowing off a site.
The discharge of pollutants from any point source into surface
waters requires National Pollutant Discharge Elimination System
(NPDES) or state equivalent permits. For a discharge permit to be
obtained for any facility, treatment of the wastes prior to discharge
may be required. All discharges of oil into United States surface waters
must be reported to the Coast Guard National Response Center in
Washington, D.C.
The Clean Water Act is the primary federal regulation govern
ng activities in wetlands (Lesniak, 1994). The act regulates dredg
ng and filling of wetlands, including the construction of access roads
and drill pads. Under the current United States policy of "no net
oss of wetlands," new wetlands may be required to be created to
obtain permits.
The act requires all nontransportation related facilities which have
discharged or could reasonably discharge oil into navigable waters to
prepare and implement a spill prevention control and countermeasure
(SPCC) plan. These plans are required for facilities that have oil
storage capacities of more than 660 gallons (16 barrels) in a single
ank or 42,000 gallons (1,000 barrels) or more in underground tanks,
SPCC plans are contingency plans for handling potential spills of
oil into open waterways. They address drainage around onshore
facilities, leak detection and prevention of storage tanks, fluid transport
and loading, facility security, pollution prevention systems, and control
devices. Each plan must be certified and reviewed every three years
by a registered professional engineer. The American Petroleum Institute
has prepared a document to assist in preparing SPCC plans (American
Petroleum Institute, 1989b).
Under the Clean Water Act, it is a crime to willfully or negligently
violate effluent limitations or conditions of a discharge permit. Fines
of up to $25,000 per day and one year of imprisonment can be imposed
or the first conviction and $50,000 and two years of imprisonment for
subsequent convictions. It is also a crime to knowingly violate the
equirements of the act or to introduce pollutants or hazardous sub
stances into a public sewer system. Fines of between $5,000 and
$50,000 per day and one to three years of imprisonment can be
Environmental Regulations
243
mposed for the first violation and double penalties for subsequent
violations. If there is "knowing endangerment" of human health or
severe bodily harm, fines of up to $250,000 and 15 years of imprison
ment can be imposed on individuals and fines of up to $1,000,000 can
be imposed on organizations. Falsifying records or tampering with
monitoring devices can result in fines of $10,000 and/or two years of
mprisonment for the first conviction and double penalties for subse
quent convictions.
Comprehensive Environmental Response, Compensation,
and Liability Act (CERCLA)
The Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA, or more commonly known as the Superfund)
was passed in 1980 and identifies sites from which releases of hazard
ous materials might occur or have already occurred. Its purpose is to
provide for the cleanup of existing waste sites and to establish a claims
procedure for affected parties. Currently, over 700 materials are
considered hazardous under CERCLA.
The act identifies potentially responsible parties (PRPs) who are
associated with each Superfund site. A PRP is anyone that may have
contributed wastes to the site, regardless of how much waste was
contributed or whether or not the waste was hazardous. A company
can also be identified as a PRP if it owned the site at one time, even
f it did not dispose of any wastes at the site or if it recently purchased
he site and has not conducted any activity on the site.
CERCLA can require any or all PRPs to clean up or pay for the
cleanup of the site, without regard to fault. The courts have imposed
oint and several liability for cleanup, which can force one PRP to
pay for the entire cleanup, even if that PRP contributed only a small
amount of nonhazardous wastes to the site. The act also allows for
costs of damages to natural resources to be charged to PRPs. Because
of the potential for significant future liability under CERCLA, there
s a strong economic incentive to properly manage solid wastes, both
onsite and offsite.
CERCLA requires most releases of hazardous substances into the
environment to be reported unless the release occurs in accordance
with a National Pollutant Discharge Elimination System (NPDES)
permit granted under the Clean Water Act.
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Environmental Control in Petroleum Engineering
Petroleum products, such as crude oil, crude oil fractions, and some
efined products like gasoline, are currently exempt from being con
sidered hazardous wastes under CERCLA. However, other wastes that
are exempt from RCRA: Subtitle C may be considered hazardous
under CERCLA, including some drilling muds and production chemi–
cals. In fact, several oilfield waste disposal sites that accepted RCRA:
Subtitle C exempt wastes have become Superfund (CERCLA) sites
because the sites were not managed properly (Fitzpatrick, 1990;
Campbell and Akers, 1990).
Under CERCLA, it is a crime to fail to notify the appropriate
ederal agency of a release of a hazardous substance into the environ
ment and to fail to notify the EPA of the existence of an unpermitted
hazardous waste disposal site. Fines of up to $10,000 and one year
of imprisonment can be imposed per violation. Penalties of $20,000
and one year of imprisonment can be imposed for knowingly destroy
ng or falsifying records required underCERCLA–
Superfund Amendments and Reauthorization Act (SARA)
In 1986, the Superfund Amendments and Reauthorization Act of
1986 (SARA: Title III) was passed, and added an emergency planning
and community right-to-know provision to CERCLA. SARA requires
owners and operators of facilities that store, use, or release hazardous
materials in volumes above a specified threshold to report information
about those materials to state and local authorities. This information
ncludes a list of all hazardous chemicals, their volumes, and Material
Safety Data Sheets (MSDS). The purpose of this information is to
assist local authorities in preparing for emergency responses. SARA
also requires releases of these chemicals above a certain amount be
eported to the appropriate agencies.
SARA was targeted primarily at industrial sites that maintain large
quantities of onsite chemicals over long periods of time. At dril
ing and production facilities, however, many chemicals, such as
drilling or workover chemicals, are present for only a few days a year
and not present at any other time. Normal operations make it very
difficult to identify the times that specific chemicals are present at any
given location.
To simplify the reporting requirements under SARA for the up
stream petroleum industry, a generic hazardous chemical category list
Environmental Regulations
245
and a generic inventory of commonly used chemicals was developed
American Petroleum Institute, 1990b). The generic hazardous chemi
cal category list is a list of chemical categories that are typically found
onsite at various times. The generic inventory indicates the maximum
amount of a material that may be onsite at any given time and how
t is stored. A generic hazardous chemical category list, with respective
hazards, and a generic inventory can be submitted to local authorities
nstead of continuously updated lists and hazards of specific onsite
chemicals. Generic lists assume that chemicals in all categories are
onsite for 365 days per year, regardless of when chemicals are
actually present. A total of 65 categories are currently in use.
SARA alters the strict liability of CERCLA by allowing new
andowners (potential PRPs) to argue that they are not liable for site
cleanup costs because they had no knowledge of the contamination
at the time they purchased the land. However, a new landowner must
prove that he had made "all appropriate inquiry" into previous owner
ship. The new owner may still be liable for cleanup if the previous
owner cannot be found or has gone out of business.
Clean Air Act
Since the Clean Air Act was initially passed in 1955 to regulate air
pollutants to protect human health and the environment, it has been
amended a number of times. The most significant amendments were
made in 1990. Unlike most other environmental legislation, the 1990
amendments of the Clean Air Act do not set safety standards for
pollutant levels; instead, the act requires standards to be set on the
maximum available control technology (MACT). Thus, the allowed
emission levels will be linked with improvements in technology, not
safety and health.
Three parts of the 1990 amendments will significantly impact
drilling and production activities: Titles 1, 3, and 5. Title 1 addresses
emissions in nonattainment areas, i.e., areas that do not meet current
air quality standards. Title 3 addresses toxic chemicals and the control
echnology required. Currently, 189 chemicals are regulated under this
act. Title 5 addresses how permits will be granted under the act. The
mpact of the 1990 amendments will not be clear until the late 1990s,
Most states have established attainment standards for the maximum
allowable concentrations of air pollutants in outdoor areas. If the
248
Environmental Control in Petroleum Engineering
ambient pollutant levels exceed those standards, permits for new
facilities that emit air pollutants will be very difficult to obtain.
Emission offsets from existing facilities will likely be required for a
permit to be obtained.
Under the Clean Air Act, it is a crime to knowingly violate any
stateimplemented pollution control plan, federal new source perfor
mance standards, hazardous air pollution standards, or noncompliance
orders. Fines of up to $25,000 per day and one year of imprisonment
per violation can be imposed for violations. It is also a crime to
knowingly make false statements, representations, or reports, or to
tamper with required monitoring devices.
Oil Pollution Act
The Oil Pollution Act was passed in 1990 to expand planning and
response activities following an accidental discharge of oil. The act
requires a Facility Response Plan to be prepared for all facilities that
could cause "substantial harm." Facility Response Plans under the Oil
Pollution Act differ from SPCC plans under the Clean Water Act in
that they address responses after a discharge has occurred, while SPCC
plans address the prevention of discharges.
Facility response plans must address emergency notification, equip
ment and personnel available for response following a discharge,
evacuation information, identification and evaluation of previous spills
and potential spill hazards, identification of small, medium, and worst
case discharge scenarios and response actions, description of discharge
detection procedures and equipment, detailed implementation plans for
containment and disposal, training procedures, a description of all
security precautions, and diagrams of facilities.
A facility normally is considered capable of causing "substantial
harm" if it has a total storage capacity greater than 42,000 gallons
(1,000 barrels) and transfers oil over water to or from vessels, or the
facility has a total storage capacity greater than one million gallons
(23,809 barrels) and meets one of the following conditions: does not
have an adequate secondary containment for each storage area, is
located where a discharge could cause "injury" to an environmentally
sensitive area, is located where a discharge could shut down public
drinkingwater intake, or has had a reported spill greater than 10,000
gallons (238 barrels) in the previous five years.
Environmental Regulations
24?
Although many drilling and production facilities do not meet these
criteria for being capable of causing "substantial harm," it is still
prudent for a response plan to be developed. If a spill occurs, having
a detailed response plan may limit some liability associated with the
spill. Not having developed a response plan could be interpreted by
the courts as negligence, even if such plans are not required.
Toxic Substances Control Act
In 1976, the Toxic Substances Control Act (TSCA) was enacted to
require the testing of chemical substances and mixtures for assessment
of risk to human health or the environment before the substances are
manufactured and distributed. This act primarily impacts the chemical
and refining industries in their development of new products and
processes that require new chemicals. This act may apply to service
companies developing improved treatment chemicals.
Under the TSCA, it is a crime to knowingly or willfully violate pro
visions of the act, use substances that were manufactured, processed,
or distributed in violation of the act, or refuse entry or inspection by
authorized agents after receiving written notification of a violation of
the act. Fines of up to $25,000 and one year of imprisonment can be
imposed per violation.
Endangered Species Act
The Endangered Species Act of 1973 prohibits actions that jeop
ardize endangered or threatened species, including the destruction
or modification of the critical habitats used by those species. An
endangered species is one that is in danger of extinction throughout
all or a significant portion of its range. A threatened species is one
that is likely to become endangered within the foreseeable future
throughout all or a significant portion of its range. This act has been
subsequently amended several times.
The Endangered Species Act has significant implications for the
petroleum industry (O'Brien, 1991). If a threatened or endangered species
is present at a site, three provisions of the act must be addressed.
First is interagency consultation, where the federal agencies that
grant permits for the oil and gas industry must consult with the United
States Fish and Wildlife Service or the National Marine Fisheries
248
Environmental Control in Petroleum Engineering
Service to determine whether the proposed action is likely to jeopar
dize a threatened or endangered species.
Second is the taking provision, where any actions that adversely
impact a threatened or endangered species is prohibited. A species is
considered to be "taken" if it is harmed, harassed, pursued, hunted,
wounded, trapped, captured, collected, or any action is undertaken to
conduct those activities. The concept of "harm" includes any actions
that significantly disrupt essential behavioral patterns.
Third is an incidental take permit, where a low level of "incidental
taking" is allowed in exchange for the development of a Habitat
Conservation Plan. A Habitat Conservation Plan specifies the impact
of the allowed level of taking, steps to minimize or mitigate taking
impacts, alternatives considered, and other measures that may be
required by the permitting agency.
Violations of the Endangered Species Act can result in a $50,000
fine per offense. Willful violations can result in criminal penalties.
Marine Mammal Protection Act
The Marine Mammal Protection Act of 1972, amended in 1988,
prohibits the taking and harassing of marine mammals. This act
regulates the use of explosives for removing offshore platforms.
Comprehensive Wetlands Conservation and
Management Act
The Comprehensive Wetlands Conservation and Management Act
of 1991 provides for management and conservation of wetlands. It
regulates activities impacting wetlands.
Hazard Communication Standard
The Hazard Communication Standard (under the U.S. Occupational
Safety and Health Administration, or OSHA) requires all employers
to identify and list chemical hazards at their facilities. The employers
are also required to provide health and safety information about those
chemicals and to educate all employees through warning labels,
Material Safety Data Sheets, and training programs.
Environmental Regulations
249
National Environmental Policy Act (NEPA)
The National Environmental Policy Act (NEPA) was adopted in
1969 to ensure that the potential environmental impact from any
proposed actions of the federal government or of the private sector
that receive federal permits have been considered. This act requires
detailed environmental reviews for major actions that may affect the
quality of the human environment. These reviews may include exten
sive environmental impact statements. The impact of actions on
threatened and endangered species must be included in the environ
mental reviews.
In addition to the federal regulations discussed above, many states
have imposed additional regulations on exploration and production
activities for the oil and gas industry. These regulations vary con–
siderably from state to state. A more complete discussion of the
regulations of individual states is found in the literature (Interstate Oil
Compact Commission, 1990; Boyer, 1990; Crist, 1990; Lynn, 1990;
Wascom, 1990; Sarathi, 1991; Smith et al., 1993).
LOCAL REGULATIONS
Local agencies—counties, cities, groups of counties—may also
regulate petroleum exploration and production activities. Typical local
regulations include those involving noise and dust
(
at a site. However, air and water pollution, including visual and
esthetic impacts, can also be regulated in cooperation with state and
federal governments.
REGULATIONS IN OTHER COUNTRIES
Most countries regulate oil and gas activities to minimize their
environmental impact. These regulations, however, may be different
from those in the United States and can vary considerable from country
to country. Many of the regulations of other countries have been
discussed by a variety of authors, as indicated in Table A3.
250
Environmental Control in Petroleum Engineering
Table A-3
Discussions of Regulations in Other Countries
Country
Alberta, Canada
Saskatchewan, Canada
India
Madagascar
Netherlands
New Zealand
United Nations
Authors
Canadian Petroleum Association (1990)
Degagne and Remmer (1990)
Mead and Lillo (1991)
Mutch (1990)
Kalra (1990)
Ratsimandresy et al. (1991)
Marquenie et al. (1991)
Meijer and Krijt (1991)
Hughes (1991)
Balkau (1990)
COST OF ENVIRONMENTAL COMPLIANCE
Although many of the environmental regulations have increased the
protection of the environment, they have also increased the cost of
producing oil. The cost of environmental compliance has been reported
to be as high as 10% of the annual expenditures of an oil field
(Chappelle et al., 1991). These high environmental costs have encour
aged the development of new technologies for waste management that
can make waste treatment and recycling more cost effective than
simple disposal (Donner and Faucher, 1990).
The potential costs of compliance with RCRA, the Safe Water
Drinking Act, the Clean Water Act, and the Clean Air Act are consider
able. Initial compliance cost estimates ranged from $15 billion to
$79 billion, with additional annual costs of $2 to $7 billion, assuming
1985 levels of industry activity (Godec and Biglarbigi, 1991). Prorating
these costs over the current United States production rates gives
an approximate incremental cost of environmental compliance of
a few dollars per barrel. Not all of these environmentally related costs
would be incurred, however, because some recovery operations would
become uneconomic and would be terminated. Between 3% and 43%
of current production would be lost from environmental regulations
with an oil price of $20 per barrel. The development of future reserves
Environmental Regulations
251
was estimated to decrease by up to 42% from the cost of environ
mental compliance.
In a separate study, the annual costs of environmental compliance
for both the upstream and downstream petroleum industry were esti
mated to range between $15 billion and $23 billion (Perkins, 1991),
That study also estimates an approximate cost of environmental
compliance of a few dollars per barrel.
If the RCRA: Subtitle C exemption for drilling and production
wastes were lost, the cost to the United States petroleum industry has
been estimated to be an additional $12 billion annually. This would
result in significant reduction in exploration and production activities
(U.S. Environmental Protection Agency, 1987).
The cost of environmental compliance must also be considered
when selling or purchasing oil and gas properties (Russell, 1989;
McNeill et al., 1993). Three areas of major concern are groundwater
contamination from production and injection wells or pits; the inability
to make property improvements because of construction requirements
and regulatory constraints; and failure to comply with existing con
struction or facilities regulations and failure to conduct monitoring and
reporting programs. The ability to obtain the necessary permits to
conduct the desired production activities must be assured before a
property is purchased.
Liability for CERCLA wastes on a property must also be considered
before purchasing the property. To minimize such liability, a staged
approach should be conducted to evaluate the potential for the property
to contain CERCLA wastes and to evaluate the potential for the site
to be declared a superfund site (Curtis and Kirchof, 1993). Detailed
and expensive sampling should be considered only if there is a signifi
cant potential for hazardous wastes to be found on the property,
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Mead, D, A. and Lillo, H., "The Alberta Drilling Waste Review Committee—
A Cooperative Approach to Development of Environmental Regulations,"
Proceedings of the U.S. Environmental Protection Agency's First Inter
national Symposium on Oil and Gas Exploration and Production Waste
Management Practices, New Orleans, LA, Sept. 1013, 1990, pp. 16.
Meijer, K. and Krijt, K., "Implications of The Netherlands' Environmental
Policy for Offshore Mining," paper SPE 23339 presented at the Society
of Petroleum Engineers First International Conference on Health, Safety,
and Environment, The Hague, Netherlands, Nov. 10–14, 1991.
Mutch, G. R. P., "Environmental Protection Planning for Produced Brine
Disposal in Southwestern Saskatchewan Natural Gas Fields," Proceedings
of the U.S. Environmental Protection Agency's First International Sympo
sium on Oil and Gas Exploration and Production Waste Management
Practices, New Orleans, LA, Sept. 1013, 1990, pp. 375386.
O'Brien, P. Y., "An Endangered Species Program: The Link Between Com
pliance and Conservation," paper SPE 23346 presented at the Society of
Petroleum Engineers First International Conference on Health, Safety, and
Environment, The Hague, Netherlands, Nov. 1014, 1991.
Perkins, J., "Costs to the Petroleum Industry of Major New and Future
Federal Government Environmental Requirements," API Discussion Paper
#070, Washington, D.C., Oct. 1991.
Ratsimandresy, R. Raveloson, E. A., and Lalaharisaina, J. V., "Environmental
and Petroleum Exploration in Madagascar," paper SPE 23344 presented
at the Society of Petroleum Engineers First International Conference on
Health, Safety, and Environment, The Hague, Netherlands, Nov. 1014,
1991.
Russell, R. M., "Environmental Liability Considerations in the Valuation and
Appraisal of Producing Oil and Gas Properties," J. Pet, Tech., Jan. 1989,
pp. 55–58.
Sarathi, P, S., "Environmental Aspects of Heavy Oil Recovery by Thermal
EOR Processes," paper SPE 21768 presented at the Society of Petroleum
Engineers Western Regional Meeting, Long Beach, CA, March 20–22,
1991.
Smith, G. E., Smith, W. R., Littleton, D. J., and Simmons, J., "Recent
Improvements in State Regulatory Programs and Compliance Practices,"
paper Society of Petroleum Engineers/Environmental Protection Agency's
Exploration and Production Environmental Conference, San Antonio, TX,
March 7–10, 1993.
Environmental Regulations
255
U.S. Department of Energy, "Environmental Regulations Handbook for
Enhanced Oil Recovery," NIPER546, Dec. 1991.
U.S. Environmental Protection Agency, "Management of Wastes from
the Exploration, Development, and Production of Crude Oil, Natural Gas,
and Geothermal Energy—Executive Summaries," report to Congress,
Washington, D.C., Dec. 1987, p. 27.
Wascom, C. D., "A Regulatory History of Commercial Oilfield Waste Dis
posal in the State of Louisiana," Proceedings of the U.S. Environmental
Protection Agency's First International Symposium on Oil and Gas Explor
ation and Production Waste Management Practices, New Orleans, LA,
Sept. 10–13, 1990, pp. 821–832.
APPENDIX B
Sensitive Habitats
Some habitats have a unique sensitivity to oil and gas production
activities and require that special operating procedures be followed to
minimize impact on them. Of particular concern are rain forests and
arctic environments.
RAIN FORESTS
Rain forests provide one of the most biologically diverse environ
ments for oil and gas operations. Because of this diversity, operations
in rain forests should be conducted with caution. Drilling muds should
be landfilled in dry, lined pits. Formation water should be reinjected,
if possible. Onsite treatment of water not reinjected should include
aeration for oxygenation and cooling, skimming of surface oil, floccu
lation and settling to remove solids, and dilution before being dis
charged into adjacent waterways (Ledec, 1990).
Precautions should be taken to prevent oil spills. Proper spacing of
valves and shutoff mechanisms can be used to minimize effects of
pipeline leaks. Pipelines should be buried to reduce the risk of vehicles
damaging pipelines along roads. Buried pipelines also require less
clearing of the forest to maintain a rightofway along the pipe. Oil
storage tanks should have permanent, earthen levees of sufficient size
to contain all of the fluids.
Road construction methods should be used to minimize damage to
surrounding trees. New camps in forested areas should use the mini
mum amount of land required for buildings, recreational purposes, and
safety. All cleared areas should be rehabilitated when the use is over.
Road construction and the subsequent colonization and conversion
of the forest by natives to agricultural uses are a major source of
deforestation. These activities can be minimized by reducing the length
of roads developed. Rivers and lakes can be used to ship goods to
256
Sensitive Habitats
257
reduce the length of roads needed. Guards along roads can also
minimize any illegal travel and limit colonization and logging.
Activities of oilfield personnel should be managed. Sufficient food
should be supplied at the site so personnel do not need to supplement
their diet locally. Fishing and hunting should be prohibited. Firearms
should be prohibited unless security needs demand it. Access of
workers to indigenous populations should also be restricted.
ARCTIC REGIONS
Because of the harsh climate, the arctic coast tundra and wetlands
are very sensitive and are slow to recover from any disturbances.
Limited sunlight, extreme cold, nutrientpoor soils, and permafrost
result in low rates of plant growth and excessively prolonged periods
of recovery. Because of these conditions, drilling and produc
tion activities must be conducted in such a way as to minimize any
adverse impact.
One difficulty with operations in the Beaufort Sea is that the
shallow waters limit access between the shore and the open sea for
transportation of supplies. This problem has been overcome by dredg
ing ports and constructing gravel causeways (Robertson, 1991). Because
causeways can alter the natural flow of water in the nearshore region,
bridges may need to be constructed to allow channels for water flow.
Ledec, G., "Minimizing Environmental Problems from Petroleum Exploration
and Development in Tropical Forest Areas," Proceedings of the U.S.
Environmental Protection Agency's First International Symposium on
Oil and Gas Exploration and Production Waste Management Practices,
Sept. 10–13, 1990, New Orleans, LA, pp. 591598.
Robertson, S. B. "Environmental and Permitting Considerations for Cause
ways Along the Beaufort Sea, Alaska," paper SPE 21764 presented at the
Society of Petroleum Engineers Western Regional Meeting, Long Beach,
CA, March 2022, 1991.
APPENDIX C
Major U.S. Chemical
Waste Exchanges
Western Waste Exchange
Arizona State University
Center for Environmental
Studies
Krause Hall
Tempe. AZ 85287
Zero Waste Systems
2928 Poplar Street
Oakland, CA 94608
(415) 8938257
California Waste Exchange
Department of Health Services
Toxic Substances Control
Division
714/744 P Street
Sacramento, CA 95814
(916) 3241818
Colorado Waste Exchange
Colorado Association of
Commerce and Industry
1390 Logan Street
Denver, CO 80203
(303) 831–7411
World Association for Safe
Transfer and Exchange
130 Freight Street
Waterbury, CT 06702
(203) 5742463
ICM Chemical
20 Cordova Street, Suite 3
St. Augustine, FL 32084
(904) 8247247
Southern Waste Information
Exchange
P.O. Box 6437
Tallahassee, FL 32313
(904) 6445516
Georgia Waste Exchange
Business Council of Georgia
181 Washington St., S.W
Atlanta, GA 30303
(404) 2232264
258
Major U.S. Chemical Waste Exchanges
259
Industrial Material Exchange
Service
IEPADLPC24
2200 Churchill Road
Springfield, IL 62706
(217) 7820450
Louisville Area Industrial Waste
Exchange
Louisville Chamber of
Commerce
1 Riverfront Plaza, 4th Floor
Louisville, KY 40202
(502) 5665000
Great Lakes Regional Waste
Exchange
Waste Systems Institute of
Michigan, Inc.
470 Market, SW, Suite 100A
Grand Rapids, MI 49505
(616) 3637367
Midwest Industrial Waste
Exchange
Rapid Commerce and Growth
Association
10 Broadway
St. Louis, MO 63102
(314) 2315555
Montana Industrial Waste Exchange
P.O. Box 1730
Helena, MT 59624
(217) 7820450
New England Materials
Exchange
34 North Main Street
Farmington, NH 03835
(603) 7554442 or 7559962
New Jersey State Waste Exchange
New Jersey Chamber of Commerce
5 Commerce Street
Newark, NJ 07102
(201) 6237070
Alkem
25 Glendale Road
Summit, NJ 07901
(201) 2770060
Industrial Commodities Bulletin
Enkarn Corporation
P.O. Box 590
Albany, NY 12210
(518) 4369684
Northern Industrial Waste
Exchange
90 Presidential Plaza, Suite 122
Syracuse, NY 13202
(315) 4226572
Piedmont Waste Exchange
Urban Institute
University of North Carolina
Charlotte, NC 28223
(704) 5972307
Ore Corporation
2415 Woodmere Drive
Cleveland, OH 44106
(216) 3714869
260
Environmental Control in Petroleum Engineering
Techrad Industrial Waste
Exchange
4619 North Santa Fe
Oklahoma City, OK 73118
(405) 5287016
Tennessee Waste Exchange
Tennessee Manufacturers
Association
501 Union Street, Suite 601
Nashville, TN 37219
(615) 2565141
Chemical Recycle Information
Program
1100 Milam Building, 25th
Floor
Houston, TX 77002
(713) 658–2462 or 6582459
InterMountain Waste Exchange
W.S. Hatch Company
643 South 800 West
Woods Cross, UT 84087
(801) 2955511
Source: B. Quan, "Waste Exchanges," in Standard Handbook of Hazardous Waste Treatment
and Disposal, H. M. Freeman (editor). New York: McGraw-Hill Book Company, 1989. Used
by permission.
APPENDIX D
Offshore Releases
of Oil
Perhaps the most obvious environmental impact from drilling and
producing oil results from offshore releases of oil. Oil slicks can be
carried over large distances and affect many miles of sensitive shore
ines. Over time, natural processes will disperse and destroy an oil
slick, but often not quickly enough to prevent damage to the shoreline.
The best response to offshore releases of oil is to minimize the amount
of oil that reaches the shoreline. This can be accomplished by mech
anically removing the oil from the water by providing a physical
barrier between the oil and shoreline and by enhancing the naturally
occurring processes that remove and degrade the oil from the water.
NATURAL DISPERSION OF OIL
When oil is spilled on open water, it is dispersed and destroyed by
a number of natural processes. These processes include spreading out
over the surface of the water, evaporation of volatile components,
dispersion of oil droplets into the water column, attachment of droplets
o suspended sediments in the water, dissolution of soluble components
nto the water column, photooxidation of hydrocarbons in the presence
of sunlight, hydrolysis, and biological degradation (Jordan and Payne,
1980; National Research Council, 1985). A simplified schematic of
hese processes is shown in Figure Dl.
When oil is spilled on water, it spreads out over the water surface
and moves with the wind and water currents. The thickness of an oil
slick is typically between 0.09 and 0.2 mm, with an average thickness
of about 0.1 mm (American Petroleum Institute, 1986a). Oil slicks are
261
262
Environmental Control in Petroleum Engineering
Figure D-1. Dispersion pathways for oil on open water.
not continuous, however; they tend to break up into long patches, with
stretches of relatively open water between each patch.
Oil released on open water is transported by local water currents.
Because these currents flow parallel to the shoreline, they tend to keep
oil slicks away from sensitive shoreline habitats. The motion of oil
slicks, however, is also affected by winds, which can blow the slicks
to shore. The average speed of a winddriven oil slick is about 34%
of the wind speed (National Research Council, 1985).
Following the release of crude oil on open water, evaporation
removes between one and two thirds of the oil from the slick during
the first few hours (Jordan and Payne, 1980). This evaporation rate,
however, depends on the oil composition, temperature, and wind.
Dissolution of hydrocarbon components can also remove some oil
from a slick. The solubility of crude oil varies somewhat with compo
sition, but the average solubility is about 30 mg/1 (National Research
Council, 1985). The most soluble components are the low molecular
weight aromatics such as benzene, toluene, and xylene. These com
pounds, however, are very volatile and are removed primarily by
evaporation. Many of the compounds that do dissolve are eventually
evaporated back into the air.
Oil slicks can be broken by surface turbulence from wind and wave
action into a floating waterinoil emulsion called chocolate mousse,
Mousse, once formed, is longlasting and very difficult to clean up.
The formation of this stable emulsion is more likely for heavy oils at
ower temperatures.
Offshore
Releases of Oil
263
Oil that is broken into small droplets can be dispersed into the water
column from turbulence as an oilinwater emulsion. Large droplets
will usually float back to the surface and be recombined with the slick.
Small droplets, however, can be taken up by marine organisms and
incorporated into fecal pellets or can be sorbed onto suspended par
ticles, particularly clays from river runoff. Because the settling rate
of suspended particulates can be low, water currents can disperse the
sorbed hydrocarbons long distances away from the spill site, keeping
their concentration at any particular location relatively low.
Oil that has been either evaporated or dissolved can be decomposed
by photooxidation when exposed to sunlight. Highenergy photons
from the sun break the hydrocarbon molecules, which then react with
oxygen, destroying the original molecule. The toxicity of partially
photooxidized hydrocarbons, however, can be higher than that of the
original hydrocarbons (National Research Council, 1985). Because the
surfacetovolume ratio for an oil slick is low, photooxidation does
not remove a significant amount of oil from the slick itself.
Some of the dissolved oil compounds can be hydrolyzed. In this
process, the normal thermal motion of the molecules in water occa
sionally breaks a chemical bond on the hydrocarbon. The broken bond
then reacts with hydrogen or hydroxyl ions in the water. The reaction
can be catalyzed by copper or calcium and can be accelerated if the
hydrocarbon is adsorbed onto suspended sediments.
Oil remaining in the marine environment will eventually be removed
by biological degradation from bacteria, yeasts, or fungi. The degrada
ion rate, however, depends on the availability of oxygen and nutrients,
such as nitrogen and phosphorus. Bacterial degradation is a major
mechanism for the eventual removal of hydrocarbons from a marine
environment, but is slow compared to other mechanisms.
Degradation rates for oil in the marine environment have been
estimated and are summarized in Table D1 (National Research Coun
cil, 1985). Under optimized conditions, degradation can be complete
n a few hours to tens of hours. The creation of optimized conditions,
however, requires enhancement of virtually all naturally occurring
conditions found in nature. Optimized conditions are never found in
nature and are virtually impossible to establish outside of the labora
ory. If a natural bacterial population has been exposed to hydrocarbons
for a prolonged period and has had an opportunity to adjust to their
presence (a long incubation period), degradation can be completed in
264
Environmental Control in Petroleum Engineering
Table 0-1
Biodegradation Rates of Oil in Marine Environment
System
Optimized seawater
conditions
Long incubation period
(natural seeps)
Short incubation period
(oil spills)
Degradation
Rate (g/m3/day)
Degradation
Time
5–2,500
0.3–144 (hours)
0.560
0.5–60 (days)
0.001–0.030
3–82 (years)
Source: National Research Council, 1985.
Copyright © 1985, National Academy of Sciences.
Courtesy of National Academy Press, Washington, D.C.
a few days to tens of days. This condition may be found around some
natural seeps. If the hydrocarbons are suddenly added to a bacterial
population from an oil spill (a short incubation period), degradation
can take years. Because of the very slow degradation rate under oil
spill conditions, bacterial degradation is not likely to play a major role
in removing oil from slicks.
ENHANCED REMOVAL OF OIL
Because natural removal processes are often too slow to prevent an
oil slick from reaching the shoreline, active measures to remove the
slick from the water may be required. These processes include mech
anically removing the oil from the open water to prevent oil from
reaching shorelines and adding materials to the slick to enhance natural
removal processes.
Mechanical Methods
Mechanical methods for removing oil from open water normally
consist of putting physical barriers between the oil and the shoreline
and using skimmers to remove the oil. Physical barriers are normally
placed to either concentrate the oil in a small area for easier removal
or to keep oil away from very sensitive shoreline habitats.
The most common physical barriers used are floating booms. Booms
are vertical sheets that extend above the water level by 4 to 12 inches
Offshore Releases of Oil
265
and below the water level by 12 to 24 inches. Booms come in various
sizes for use with different wave heights and wind speeds. For sensi
tive wetlands with very shallow water, earthen dikes could be con
structed as a temporary barrier.
A variety of skimmers are available to mechanically collect oil.
Skimmers often use oilwet sorbent materials like polyurethane or
polypropylene to collect the oil. These sorbent materials can absorb
many times their weight in oil without collecting much water,
Booms and skimmers are most effective when the waves, wind, and
currents are low and when used very soon after the oil has been
released. Even under ideal conditions, this equipment is most effective
on relatively small spills. In heavy seas or for very large spills, these
methods are usually ineffective. Because booms and skimmers are most
effective when they are employed very soon after oil has been released,
they should be stockpiled near potential release points. A suitable
means of rapidly transporting and deploying them is also needed.
Chemical Dispersants
Natural removal processes are accelerated if an oil slick is broken
into a large number of smaller droplets. Wind and wave action natur
ally break up a slick into droplets, but the resulting droplets can easily
coalesce back into larger patches of oil. This coalescence can be
inhibited by adding chemical dispersants. Most dispersants are surfac
tants that lower the interfacial tension between the oil and water.
Using dispersants has some important advantages for environmental
protection. Oil dispersed into the water column is swept away by the
currents and is not easily blown to shore by winds. Dispersants also
inhibit the formation of mousse, making the removal of nondispersed
oil easier. Dispersants also reduce the tendency of oil to stick to solid
surfaces (including suspended particulates, fish eggs, and shoreline
rocks), making any subsequent shoreline cleanup easier. Dispersants
have also been shown to significantly lower the uptake of oil by
suspended sediments (American Petroleum Institute, 1985).
Dispersants, however, do have some disadvantages. They tempo
rarily create a higher concentration of oil in the water column beneath
the slick, increasing the impact to biota in the water column. Although
some of the older dispersants were toxic, many modern dispersants
are less toxic than the oil they disperse. Thus, dispersants increase the
266
Environmental Control in Petroleum Engineering
shortterm impact within the water column, but minimize the longterm
impact of oil reaching sensitive shorelines. The short and longterm
environmental impacts of using dispersants must be balanced when
considering their use. For spills with little likelihood of reaching
sensitive shoreline habitats, the use of dispersants may not be neces
sary. For spills occurring in deep water that are threatening sensitive
shoreline habitats, the use of dispersants may be very beneficial.
A number of field trials of dispersants have been conducted, Disper
sants have been found to be effective in accelerating the dissipation
of oil slicks and reducing the longterm impact of released oil. The
method of application (boat or airplane) and the time the dispersant
was applied after the oil release affected the results (American Petro
eum Institute, 1986b). For nearshore applications, the use of disper
sants was found to lower the uptake of oil by mollusks (American
Petroleum Institute, 1986c). In a study on oil released in mangrove,
seagrass, and coral reef habitats, dispersed oil was observed to have
a lower impact in the intertidal zone than undispersed oil, but it had
a higher impact in the subtidal zone (American Petroleum Instit
ute, 1987b).
Dispersants have been applied to several oil slicks, but their results
have been inconclusive. Because there was no control during such
applications, it has not been possible to determine whether the disper
sants actually minimized the environmental impact of the oil.
Dispersants were improperly used on oiled shorelines following the
Torrey Canyon tanker accident in 1967. High concentrations of toxic
solventbased cleaners were applied directly to the shoreline to remove
he oil. These toxic dispersants severely impacted intertidal organisms
and significantly delayed the recovery of the area following the spill.
The toxicity of these dispersants, however, resulted more from the
aromatic hydrocarbonbased solvents used with the dispersants than
rom the dispersants themselves.
A number of lowtoxicity dispersants have been developed since the
Torrey Canyon accident. Bioassays have been conducted on a number
of these dispersants and are summarized in Table D2 (Wells, 1984).
By comparing these toxicities with those for various hydrocarbons
described in Chapter 3, it can be seen that the toxicity of modern
dispersants is considerably lower than that of many hydrocarbons.
To be most effective, dispersants need to be applied within a day
or two following the release of oil. However, because of the improper
Offshore Releases of Oil
267
Table D-2
Toxicity of Dispersants
Species
nvertebrates
Stony Coral
Ologochaete
Intertidal Limpet
Crustaceans
Amphipods
Mysids
Brown Shrimp
Grass Shrimp
Dispersant
Shell LTX
Corexit 7664
Finasol OSR2
Finasol SOR5
BP1100X
BP1100WD
Various
Various
Various
Various
Various
Corexit
waterbased
oilbased
waterbased
oilbased
7664
AtlanticPacific
Gold Crew
Nokomis3
Fish
Larvae
Gobies
Stickleback
Dace
Coho Salmon
Killifish
Corexit 7664
Shell LT
Various waterbased
Various oilbased
Various waterbased
BP1100X
AP
96-hr LC.
162 (1 day)
> 1,000
> 1,000
> 1,000
3,700
270
> 10,000
200 + 130
>4,500
150
2,80010,000 (48 hrs)
> 10,000 (27°C)
> 100,000 (17°C)
1,000 (27°C)
1,800 (17°C)
150 (27°C)
380 (17°C)
140 (27°C)
250 (17 0 C)
400
460
950+ 250
10,000
1,400
1,700
100 (2 days)
*Unless otherwise noted.
ource: after Wells, 1984.
Copyright ASTM. Reprinted with permission.
application of dispersants following the Torrey Canyon accident,
getting regulatory approval to use dispersants on oil spills can be
difficult to obtain in a timely manner. A detailed contingency plan for
he use of dispersants should be developed and submitted to regulatory
agencies for review and approval prior to any spill to enhance the
268
Environmental Control in Petroleum Engineering
likelihood of their being approved after a spill has occurred (American
Petroleum Institute, 1987a).
Enhanced Photo-oxidation
Recent studies have shown that photooxidation of an oil slick can
be significantly enhanced by adding titanium dioxide particles to the
slick. Titanium dioxide acts as a catalyst to break the hydrocarbon
bonds and accelerate oxidation (Gerischer and Heller, 1991 and 1992),
Bioremediation
Bioremediation has been proposed as a method of accelerating the
dispersion of oil slicks on open water. As discussed in Chapter 6,
bioremediation of hydrocarboncontaminated soils can take several
months for significant biological degradation of the hydrocarbons to
occur, even under optimum conditions. Keeping the optimum combina
tion of bacteria and nutrients in contact with oil on open water for
more than a few hours is unlikely. Because of this, bioremediation is
not believed to be effective in degrading oil slicks. A test of open
water bioremediation was conducted following the Mega Borg accident
(Oil and Gas Journal, 1990), but this test was considered inconclusive
by most scientists because there was no control.
REFERENCES
American Petroleum Institute, "Surface Chemical Aspects of Oil Spill Sedi
mentation," API Publication 4380, Washington, D.C., April 1985.
American Petroleum Institute, "The Role of Chemical Dispersants in Oil Spill
Control," API Publication 4425, Washington, D.C., Jan. 1986a.
American Petroleum Institute, "The Role of Chemical Dispersants in Oil Spill
Control," Washington, D.C., Jan. 1986b.
American Petroleum Institute, "Tidal Area Dispersant Project," API Publica
tion 4440, Washington, D.C., July 1986c.
American Petroleum Institute, "Developing Criteria for Advance Planning for
Dispersant Use," API Publication 4450, Washington, D.C., April 1987a.
American Petroleum Institute, "Effects of a Dispersed and Undispersed
Crude Oil on Mangroves, Seagrasses, and Corals," API Publication 4460,
Washington, D.C., Oct. 1987b.
Offshore Releases of Oil
269
Gerischer, H. and Heller, A., "The Role of Oxygen in Photooxidation of
Organic Molecules on Semiconductor Particles," J. Phy. Chem., Vol. 95,
1991.
Gerischer, H. and Heller, A., "Photocatalytic Oxidation of Organic Molecules
at TiO2 Particles by Sunlight in Aerated Water," J. Electochem. Soc., Vol.
139, No. 1, Jan. 1992.
Jordan, R. E. and Payne, J. R., "Fate and Weathering of Petroleum Spilled
in the Marine Environment: A Literature Review and Synopsis," Ann Arbor
Science Publishers, Ann Arbor, MI, 1980.
Oil and Gas Journal, Aug. 6, 1990.
National Research Council, Oil in the Sea: Inputs, Fates, and Effects,
Washington, D.C.: National Academy Press, 1985.
Wells, P. G., "The Toxicity of Oil Spill Dispersants to Marine Organisms: A
Current Perspective," in Oil Spill Chemical Dispersants: Research, Experience, and Recommendations, T. E. Allen (editor), STP 840, American
Society for Testing and Materials, Philadelphia, PA, 1984.
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Index
Abandoned wells, 141
Acid retarders, 47
Acidizing, 46–48
Acoustic impacts, 127128
Adsorption, 179, 188, 195
Air pollution, 5759, 126–127,
142, 190, 194
Amines, 26, 29, 45, 47–48,
50–51, 53
Annular injection, 208, 210
Arctic, 149, 210, 257
B
Barite, 3, 22, 24, 2930,
157158, 225
Beneficial use, 121, 204
Bioassays, 7177, 83, 8889,
99, 104, 106, 114, 117, 266
Biocides, 26, 30, 32, 45, 50, 52,
106, 159
Biological degradation, 173, 178,
180, 184, 188, 191193, 205,
221, 224, 261, 263, 268
Bioremediation, 8, 191193,
224, 268
Booms and skimmers, 264
BTEX, 58, 85, 87
Carbon dioxide, 26, 43, 46, 49,
5152, 59, 176, 191, 192
Centrifuges, 176, 181–182,
186–187
Clay, 3, 2129, 33, 35, 4550,
96–97, 141, 159, 182, 188,
191, 194, 211, 224–225, 263
Coagulants, 106
Combustion, 1819, 53, 5758,
9495, 160, 190, 194196
Contingency plans, 163
Contractors, 156
Cooling towers, 52
Corrosion, 2530, 32, 4352,
60, 106, 159, 180, 189
Costs, 1114, 28, 34, 61, 77,
117, 126, 144, 150155,
172, 182190, 204, 208,
220224, 243, 245,
250251
D
Deflocculation, 23, 30, 33
Density control, 24, 2930, 32,
155
Dispersants, 265
Disposal, 9, 26, 34–35, 38, 119,
154, 162, 172, 190, 194,
203–211, 224, 234, 236,
244
Dissolved solids, 35, 40, 44,
5253, 56, 96, 100,
182186, 193, 203204,
208, 216, 240
Distillation, 184, 189, 191
271
72
Environmental Control in Petroleum Engineering
Drilling fluids
oilbased, 27–29, 117, 120,
156, 205
purpose, 20
toxicity, 6, 106120, 156
waterbased, 21–27
Drilling process, 1920
Drilling wastes, 3, 152
E
Ecosystems, 91
Electric fields, 178
Emulsions, 28, 40, 43, 4750,
106, 157, 162, 173, 176–178,
189, 242, 262263
Environmental audit, 7, 144149
Evaporation, 8, 149, 179, 184–186,
194, 204, 221, 261–262
Excavation, 224
Exposure limits, 75, 95, 101, 125
Filters, 5153, 160161, 177,
181, 184, 186
Filtration, 177, 181, 186, 193
Flocculation, 23, 29, 33, 45,
178, 181183, 256
Fluid loss, 50
Foam, 46
Formation damage, 27, 29, 49
Freeze protection, 53
Friction reducers, 48, 50
Fugitive emissions, 60–64, 160, 195
Gas flotation, 176
Gas treatment chemicals, 106
H
Heater treaters, 176, 189
Heavy metals, 53, 119, 140,
182, 190, 194, 205, 207,
210
produced water, 41
reserves pits, 35
sources, 3032
toxicity, 100105
Human health, 94, 124
Hydrates, 52
Hydraulic fracturing, 48–51
Hydrocarbons
families, 7883
produced water, 41
toxicity, 8396
Hydrocyclones, 174, 186
Hydrogen sulfide, 51
I
Incineration, 190
Ion exchange, 52, 182, 225
Land treatment, 205
Lost circulation, 24
Lubricants, 25, 53
Lubrication, 160
M
Marine animals, 89
Material Safety Data Sheets,
7677, 244
Mechanical integrity tests, 208,
241
N
National Pollutant Discharge
Elimination System, 115,
242, 243
Natural gas, 51–52, 57
Neutralization, 185
Nitrogen dioxide, 57, 195
NORM, 6, 56, 126, 146, 211
Nuclear radiation, 5457, 121126
O
Offshore platforms, 128, 211
Oil slicks, 261
Oxidation, 180, 195
Oxygen depletion, 42
Paraffin inhibitors, 106
Particulates, 196
Percolation, 8, 186, 204
pH, 25, 49, 140, 185, 234
Photooxidation, 263, 268
Pipe dope, 30
Plate separators, 174
Precipitation, 180, 183
Produced water, 152
hydrocarbons, 41
metals, 41
process, 39
Production chemicals, 43
toxicity, 105106
Profile modification, 48
Pump and treat, 222
Pyrolysis, 189
R
Radioactive decay, 121
Index
273
Radioactive tracers, 55
Rain forests, 256257
Recycling, 161162
Regulations, 10, 230, 249
Clean Air Act, 245246
Clean Water Act, 241–243
Comprehensive Environmental
Response, Compensation,
and Liability Act, 243244
Comprehensive Wetlands
Conservation and
Management Act, 248
Endangered Species Act, 247248
Hazard Communication
Standard, 248
Marine Mammal Protection
Act, 248
National Environmental Policy
Act, 249
Oil Pollution Act, 246247
reserves pits, 38
Resource Conservation and
Recovery Act, 149, 231240
Safe Drinking Water Act, 240–241
Superfund Ammendments and
Reauthorization Act, 244–245
Toxic Substances Control Act,
247
Reinjection, 52, 156, 207
Remediation, 9, 64, 216, 220
Reserves pits, 35, 119, 154,
186187, 210, 225
Reverse osmosis, 184
Risk assessment, 8, 128–131, 217
Road spreading, 207
Salt, 32, 119, 182, 204, 205,
207, 210, 225
274
Environmental Control in Petroleum Engineering
toxiclty, 5, 96100
Sand, 51, 53
Scale, 44, 56
Scrubbers, 5253, 195, 196
Segregation, 8, 153
Separations, 8, 33, 39, 51, 53,
160, 172173, 181
Site assessment, 216
Site preparation, 38, 153, 205,
256
Solidification, 193
Solvents, 48, 190, 192, 266
Spill prevention control and
countermeasure plans, 242
Steam injection, 53, 58, 194, 223
Substitution, 29, 156–159
Sulfur, 225
Sulfur dioxide, 44, 53, 57, 127,
195
Supercritical fluids, 191
Surfactants, 26, 29, 40, 4349,
106, 157, 188, 192, 222, 265
Toxicity, 4, 5, 71, 234, 263, 266
air pollution, 126–127
drilling fluids, 6, 106–120
heavy metals, 6, 100–105
hydrocarbons, 8396
nuclear radiation, 121,
123126
produced water, 120–121
production chemicals, 105106
salt, 5, 96–100
Training, 165
Treatment, 8, 162, 172
U
Ultraviolet irradiation, 180
V
Viscosity, 21, 28, 49, 50
Vitrification, 194
Volatile organic carbon (VOC),
57, 65, 161, 179, 194, 206,
216, 223
Volatilization, 179, 223
W
Washing, 188, 222
Waste management plans, 7, 144,
149
Waste migration, 139, 221
Waste minimization, 150–161
Water vapor, 51
Wettability, 48