Drilling fluid regulations outside Latin America by oym20829

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									Offshore Oilfield Ecotoxicity Testing: An Overview

              John Hall, J. Michael Wilson, and Arron Karcher, Halliburton



                                  ABSTRACT
        One of the key tools used by environmental regulators in the control of use and
discharge of offshore well construction chemicals is the application of ecotoxicity testing.
This testing may be required as part of a “clearing house” approach where chemicals are
pre-registered before use, or alternatively as “end of pipe” effluent testing with samples
being collected at the rig site.

        Biodegradation, aquatic toxicity, and bioaccumulation are the mainstays of many
regulatory programs, and the tests used differ significantly between regions and
industries. During product evaluation, ensuring that appropriate test results are being
examined is critical. This paper discusses differences in test methods and what these
differences can mean to the end results and applicability of a particular test. Finally,
approaches taken in testing offshore chemicals for use and discharge in the U.S. and
European offshore arenas are compared.




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                             INTRODUCTION
Oil Industry Environmental Regulations and Policy: Why
Regulate?
        The requirement for countries to regulate the use and discharge of drilling fluids
has been the result of a number of drivers. One such driver for marine resources may be
the perceived conflict among various stakeholders. For example, the needs of the oil,
tourism, and fishing industries may compete with one another. Each industry may be very
wary of the others’ activities. This wariness may be founded in negative past experiences,
lack of understanding, or any of a wide range of reasons. Applying regulations may
implement controls to safeguard each stakeholder’s interests.

        In addition to internal pressures to regulate by concerned stakeholders, some
countries have signed international conventions, which means that they have to bring
about legislation in compliance with their obligations. Examples of this type of regulation
are the Oslo and Paris Commission (OSPAR), which impacts the North East Atlantic, the
Barcelona Convention, which covers the Mediterranean Sea, and the Helsinki
Commission (HELCOM), which covers the Baltic Sea.

Measuring Environmental Impacts of Oilfield Activities
        As a result of the nature of chemicals in use in the drilling fluids industry, the
environment can be impacted by both uncontrolled releases and controlled releases of
waste as a disposal route. To minimize the impacts of either intentional or unintentional
discharges, drilling fluid suppliers have endeavored to minimize the environmental
impacts of the chemicals they use. However, the minimization of environmental impact
must be considered in conjunction with the technical performance of the fluids used. The
very products that have a strong technical appeal may be the ones that show the greatest
impact because of the action of the active ingredient. For example, a particularly effective
surfactant may also show higher toxicity than a less effective surfactant. If lower volumes
of the active material are used, the impacts on the environment when the material is
discharged can be reduced. If “green chemicals” are less effective than conventional
counterparts, then environmental impact and technical performance must be balanced.

        To study and determine the potential environmental impact of a product or
material, it is clearly unreasonable, wasteful, and harmful to apply it to the environment
into which it may be released; therefore, a series of surrogate tests have been derived.
These tests are aimed at examining the following ecotoxicological characteristics of the
material:

        •   Toxicity
        •   Biodegradability
        •   Bioaccumulation potential


                                   TOXICITY
        Many materials will show toxicity to plant or animal life if applied in sufficient
quantities. This toxicity may even come from commonplace materials that the human
race may consider as foodstuff. In the context of drilling fluid chemistry, chemically

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active materials such as emulsifiers, alkalinity modifiers, and thinners are expected to
show greater toxicity than more inert materials such as mineral powders, polymeric gels,
and lost-circulation fibers. Therefore, prioritizing the assessment of some chemicals
above others is important. After a thorough investigation, materials that are especially
toxic may even be flagged as candidates for substitution by some governments. Fluids
suppliers then face the challenge of producing materials that show good environmental
acceptability without any trade-off in technical performance.

How Do We Measure Toxicity?
        The toxicity of materials can be measured in two principal ways. First, we can
examine the lethal effect of a material by measuring the concentration at which it
becomes so toxic that it causes death in a population of animals. Alternatively, we can
use more subtle sub-lethal tests and observe changes in an animal’s behavior at a certain
concentration of test substance, e.g., changes in breathing or feeding rate, or altered
reproductive output. These two forms of toxicity tests are referred to as LC50 and EC50,
which represents Lethal Concentration or Effective Concentration that affects 50% of the
population being observed.

        When conducting a study of a material’s toxicity, considering that material’s
environmental fate is always important. For example, when examining marine discharges
of something that is insoluble and denser than water, we should examine the potential
impact on seafloor-dwelling animals. In contrast, if our test substance is soluble, it will
remain in the water column, so we may want to examine the toxicity of that substance
using animals that live in the water column. This is important when considering what we
may expect the impacts of drilling fluids to be. Invert emulsion drilling fluids, if
discharged to the sea, especially on the surface of cuttings, will sink to the seafloor. In
contrast, water-based drilling fluids tend to be dispersed throughout the water column.
Therefore, we should ensure that the toxicity test for the drilling fluid matches the
environmental fate of that fluid.

         We know that drilling fluids can be tested using a variety of methods, but what
do the results look like? Commonly, we will take a range of concentrations of the test
substance and then expose our organisms to that substance. A number of replicates (sets
of animals) are exposed to each concentration, so that we can account for the biological
variability as much as possible. Table 1 gives a typical set of results of a toxicity test.

         We can see that the test uses five replicates, with 20 animals in each replicate,
and a range of test concentrations from 0 to 100,000 ppm. Generally, the animals in the
0-ppm concentration did not suffer mortalities, while in the highest concentration of
100,000 ppm, no survivors (100% mortality) were recorded. If we plot the data, we can
see the relationship between toxicity/mortality and concentration (Figure 1). The LC50 in
this case is around 28,000 ppm. Usually, software is used instead of graphical methods to
calculate the LC50 value.

         The species used for toxicity testing in Europe under OSPAR requirements
include a sediment bioassay using amphipod crustacean Corophium volutator, a fish
toxicity test using juvenile Scopthalamus, toxicity to marine copepods using Acartia, and
a marine algal growth inhibition test using Skeletonema costatum. In the United States,
sediment toxicity tests are carried out using the amphipod Leptocheirus plumulosus as the
test organism. Suspended particulate phase (water column) toxicity tests are carried out
using the Mysid shrimp (Americamysis bahia).


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        Tests are not always confined to aquatic media. In some areas, toxicity tests have
also been performed on soils. For example, wastes have been mixed into soil, and the
germination and subsequent growth of plants and survival of earthworms has been
observed.

                           BIODEGRADATION
        The degradation of chemical products in the environment may occur by several
pathways, all of which are sometimes collectively, but erroneously, called biodegradation
(1). These different pathways or mechanisms have been defined in various ways.
However, the definitions provided by ASTM (American Society for Testing and
Materials) are generally consistent with all others (2). Chemical products may degrade
through the process of hydrolysis (cleavage by water), oxidation, photodegradation (and
fragmentation), and biodegradation.

         Biodegradation is defined for the purposes of this discussion as the degradation
that results from naturally occurring organisms such as bacteria, fungi, or algae. With the
exception of hydrolysis, these mechanisms are all forms of chemical oxidation.
Hydrolysis is not per se oxidation; however, the action of hydrolysis may allow oxidation
to occur more easily.

        The complete oxidation of an organic substance is referred to as mineralization.
For pure organic hydrocarbons, the products of mineralization are carbon dioxide (CO2)
and water (H2O). Complete mineralization of organic chemicals is possible with
biodegradation.

         Once a substance, whether toxic or not, has been intentionally or unintentionally
discharged to the environment, unless that material is naturally occurring, it preferably
should degrade to something less toxic or a material that is naturally occurring.
Mineralization to CO2 and H2O is even more desirable. One example may be that of drill
cuttings piles. It is clearly undesirable for the base fluid in drill cuttings to still be present
in sediments on the seafloor underneath an offshore rig several years after drilling has
ceased. A more favorable outcome is for the base fluid to completely degrade, i.e. to CO2
and H2O, and for near-field and far-field sediment hydrocarbon concentrations to be
indistinguishable. We may even be able to enhance disposal sites by designing fluids that
have beneficial effects while breaking down. For example, in a land-farming situation, it
may be useful to have fluids that will break down and release plant nutrients such as
nitrogen, potassium, or phosphorus in controlled amounts when the material is spread to
land.

How Do We Measure Biodegradation?
         As for the toxicity test, the fate of the substance must be considered when
designing an investigation into biodegradation of a substance. If its fate is the seafloor,
running a test of the substance mixed into sediment and submerged in seawater is
appropriate. If the material will be spread onto land, it should be mixed into soil and
tested in air, or at least tested in fresh water.

        Unfortunately, many of the early tests for biodegradation used in the oilfield
were “borrowed” from other industries, and the results of these tests are not always
appropriate. For example, the household and industrial surfactant industry was concerned
about the persistence of laundry and household soaps and detergents in the early 1960s.

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These materials were not being degraded in sewage treatment plants and were finding
their way to the environment where they caused foaming and toxicity problems. A test
was devised in which the materials were combined with freshwater and sewage treatment
plant bacteria. This test modeled the system into which the detergents were placed, but
the method is a poor way of examining the environmental fate of drilling fluids. The
inclusion of sewage plant bacteria can give a misleading result if we are examining
drilling fluids because drilling fluid materials will not find their way to a sewage
treatment plant for treatment.

         Sometimes, drilling fluid components will end up on land or in the water column
(for example water-based fluids) where oxygen is available, and sometimes the fluid
components will be buried in the seafloor where very little to no oxygen is present.
Therefore, two groups of tests are used in determining biodegradation of drilling fluid
components. One is the aerobic test, which is always run in an excess of oxygen; the
other is an anaerobic test, which is run in the absence of oxygen.

        The most recently developed biodegradation test for drilling fluids is the U.S.
modification of ISO 11734. The U.S. EPA has adopted this test as the appropriate
biodegradation test for synthetic-based fluids. The base fluids to be investigated are
mixed with marine sediments under conditions where oxygen is purged from the system.
Water is added. An indicator of oxygen presence is added to show if aerobic conditions
exist. Bottles are incubated in the dark, and the volume of CO2 produced is measured
periodically. A control sample is run. Using the difference between gas volumes
produced in control and experimental bottles, in conjunction with knowledge of the
carbon content of the base fluid, the percentage theoretical biodegradation can be
calculated.

        For other chemicals used in the drilling industry, especially in offshore
operations, a major concern is aquatic biodegradability. More degradation pathways are
available in landfills or through other disposal methods such as composting. Landfills and
composts typically have greater concentrations of microorganisms and microorganism
types. Therefore, degradation may occur more readily than in aquatic environments.

         The aquatic environment is considered by many to be less “robust” and therefore
less biologically active than on-land degradation. A number of recognized procedures are
available for determining aquatic biodegradability in waters, both fresh water and
seawater. These methods may rely entirely on native bacteria as the degrading species or
they may allow active bacterial culture to be added to the test solution. The more
stringent of these methods use only the native bacteria population for the test. For
example, European regulators call for use of OECD Guideline for Testing of Chemicals
306 (1992), which is a natural seawater, closed-bottle method that is run aerobically.
Only the native bacteria present in the natural seawater are responsible for the
biodegradation.

         Regardless of the method used, the biodegradability of a substance is expressed
as a percentage of a maximum amount possible. As an example, the aerobic biological
oxygen demand (BOD) is measured for dilute solutions of the test chemical. This amount
is then expressed as a percentage of the theoretical oxygen demand (ThOD). The ThOD
is a calculation method appropriate for pure or well characterized substances, i.e., by
complete elemental analysis. Alternately, for less well characterized or less well known
test substances, the measured chemical oxygen demand (COD) may be used to calculate
the biodegradability. A popular method for measuring the COD is the dichromate reactor


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digestion method (3). This method is approved by the U.S. EPA for waste-water analysis
(4).

         A variety of test methods are available to measure the aquatic aerobic BOD.
These may use oxygen uptake as a measure of the BOD demand or, more commonly, the
depletion of dissolved oxygen (DO) is used to measure the BOD for dilute solutions of
the test substances. Very simply, dilute solutions (2 to 6 ppm) of the test chemicals are
sealed in special bottles and incubated at a specified temperature, often 20°C. Samples
are pulled from the incubator periodically and the change in DO is measured using a DO
probe and meter. This change is then compared against blanks containing no test
chemicals. Each procedure has a specific regimen for calculating the BOD.

        Figure 2 shows a typical aquatic biodegradation curve for a test substance. Also
shown in the graph is the biodegradation curve for a reference substance, in this case
sodium benzoate. Biodegradation of a suitable reference material is always performed
along with the test substance to ensure that the water contains a viable bacterial
population. The value for the reference biodegradation is not used to calculate the test
substance biodegradation, but rather serves only as a visual reference of viability.
European regulators require that all the ecotoxicological testing be performed by a Good
Laboratory Practices (GLP) certified laboratory.

                        BIOACCUMULATION
         Bioaccumulation is generally defined as the process through which a chemical
increases in concentration in a biological organism over time when compared to the
concentration of the chemical in the environment. Compounds accumulate in living
things any time they are taken up and stored faster than they are broken down,
metabolized, or excreted. The extent of bioaccumulation depends on the concentration of
the chemical in the environment, the amount of chemical coming into an organism from
the food, air, or water, and the time it takes for the organism to acquire the chemical and
then store, metabolize, degrade, and excrete it. The nature of the chemical itself, such as
its solubility in water and fat, also affects its uptake and storage in organisms. The
bioaccumulation can be measured using actual organisms, but this type of measurement
is very time consuming and costly, so a surrogate fat is used. Most often the surrogate fat
is n-octanol, and the bioaccumulation of a chemical is measured/predicted indirectly
through a chemical’s partitioning between n-octanol and water (Pow).

         Pοw is a key parameter in studies of the environmental impact of chemical
substances. A highly significant relationship has been shown between the Pοw of
substances and their bioaccumulation in fish (5-7). Pοw is also useful in predicting
adsorption on soil and sediments and in establishing quantitative structure-activity
relationships for a wide range of biological effects.

        One method that directly measures this partitioning coefficient is OECD
Guideline for Testing of Chemicals No. 107, called the Partition Coefficient (n-
octanol/water): Shake-Flask Method (8). This method is based on the principle that the
Nernst partition law applies at constant temperature, pressure, and pH for dilute solutions.
OECD Guideline No. 107 states that the law strictly applies to a pure substance dispersed
between two pure solvents when the concentration of the solute in either phase is not
more than 0.01 mole per liter. If several different solutes occur in one or both phases at
the same time, the results may be affected. Dissociation or association of the dissolved
molecules causes deviations from the partition law. In general, the partition coefficient


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(Pow) is the ratio of the equilibrium concentrations of a dissolved substance in a two-
phase system consisting of two largely immiscible solvents. For n-octanol and water, the
partition coefficient is the quotient of the concentrations of the two, expressed as follows,
but usually written in the form of its logarithm to base ten:
                                               Cn − octanol
                                       Pow =
                                                Cwater

         High-performance liquid chromatography (HPLC) is another method used for
measuring/predicting bioaccumulation and is outlined in OECD Guideline for Testing of
Chemicals No. 117, concerning the Partition Coefficient (n-octanol/water), HPLC
Method (9). This test is performed on analytical HPLC columns packed with a
commercially available solid phase containing long hydrocarbon chains (e.g., C8-C18)
usually chemically bound onto silica. Chemicals injected onto such a column move along
it by partitioning between the mobile solvent phase and the hydrocarbon stationary phase.
The chemicals are retained in proportion to their hydrocarbon-water partition coefficient,
with water-soluble chemicals eluting first and oil-soluble chemicals eluting last. From
retention time measurements, the capacity factor (k) for each solute can be calculated by:


                                         k=
                                               (tr − t0 )
                                                  t0

where tr is the retention time of the test substance, and tο is the dead-time, i.e., the average
time an unretained molecule needs to pass through the column. In this method,
quantitative analytical methods are not needed. Only the retention time of the substance is
measured and the capacity factor of the substance is compared to chemicals that have a
known published logPow value. When using either OECD 107 or 117 to measure a logPow
value, OSPAR states that a logPow of 3.0 or greater has the potential to bioaccumulate.

Quality of Material
        The existence of tests to investigate toxicity, biodegradation, bioaccumulation,
and other characteristics that can cause environmental impact means that regulators can
reduce or minimize environmental impacts by insisting that materials meet certain
standards of biodegradation and toxicity before they can be discharged, or even used in
certain environments. Regulators can identify the Best Available Technology (BAT) by
comparing test performance or ranking materials in terms of environmental performance.

Quantity of Material
         However innocuous a material is in terms of toxicity and biodegradation,
minimizing the amount of material that is discharged is generally best. This waste
minimization is usually in the interest of the operator, especially when expensive
materials such as synthetic-based fluids are used. In this case, governments may rely on
the cost savings achievable by minimizing discharges as a regulatory tool. Alternatively,
restriction can be placed on the amounts of fluid that can be retained on drill cuttings.
This restriction has been enforced in the U.S., with the EPA using data on performance of
various cuttings drying and cleaning equipment to set limits at which synthetic-based
fluids can be discharged on drilled cuttings.

Stock Limitations vs. Rig Site Regulation

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         Some regulators ask that chemicals be tested before they can be used. Others
prefer to examine what is discharged, i.e., “end of pipe” regulations. A clear dichotomy
exists in the U.S. and Europe over the issue of stock vs. discharge limitations. While
discharge limitations measure the direct toxicity of materials as they are discharged, the
repeated testing and uncertainty of compliance while operations are continuing is a
drawback. The cost of this testing activity is borne mainly by the operators. In contrast,
the stock limitations allow operators to seek permission to discharge materials before use
and, in the absence of discharge limitations, are more confident of compliance with
permits to operate, while the service companies pick up the costs of testing.

           SUMMARY AND FUTURE TRENDS
        Though individual countries have been active in developing their own
environmental regulations, the strategy adopted by European regulators, and to a lesser
extent, U.S. regulators, has had a significant influence. Since the late 1990s/early 2000s
when European regulators barred the discharge of invert emulsion fluids, countries
developing regulations and seeking direction on minimizing impact of invert emulsion
systems on the environment have been more strongly influenced by the U.S.

         The future of drilling fluids and discharge regulations will include the imposition
and possibly tightening of use and discharge regulations. A number of countries that are
significant producers of hydrocarbons still have minimal environmental regulations. They
are currently assessing the regulatory tools available, and in consultation with other
governments, industry specialists, and operator and service companies, such countries are
gradually building a portfolio of laws, guidelines, local bioassay facilities, and trained
technicians to ensure that impacts of drilling activities are minimized.




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Appendix 1. Summary of tests required by European and US Regulators
                                                                                    Applicability
Test Type            Test Name                                                     USA    Europe
Biodegradability
                     OECD Guideline for testing of Chemicals 306 (1992).                     ●
                     Biodegradability in Seawater, Closed Bottle Method.
                     Modified ISO11734:1995 method: Water quality -                 ●
                     Evaluation of the ‘ultimate’ anaerobic biodegradability of
                     organic compounds in digested sludge - Method by
                     measurement of the biogas production (1995 edition).
Toxicity
                     PARCOM (1995), A sediment bioassay using an                             ●
                     amphipod Corophium sp. Oslo and Paris Commissions
                     Protocol.
                     Paris Commission (PARCOM 1995). Protocol for a Fish                     ●
                     Acute Toxicity Test. Oslo and Paris Commission
                     Protocol.
                     OECD Guideline for Testing of Chemicals 203 (1992).                     ●
                     Fish, Acute Toxicity Test.
                     ISO 14669:1999(E) Water Quality - Determination of                      ●
                     Acute Lethal Toxicity to Marine Copepods (Copepoda,
                     Crustacea).
                     EN ISO 10253 : 1998 Water Quality - Marine Algal                        ●
                     Growth Inhibition Test with Skeletonema costatum and
                     Phaedodactylum tricornutum
                     OECD Guidelines for the Testing of Chemicals Method                     ●
                     201 - Alga Growth Inhibition Test
                     ASTM E1367–92 method: Standard Guide for Conducting            ●
                     10-Day Static Sediment Toxicity Tests with Marine and
                     Estuarine Amphipods. Leptocheirus plumulosus as the test
                     organism and sediment preparation procedures specified
                     in Appendix 3 of 40 CFR 435, Subpart A.
                     “Suspended Particulate Phase Toxicity” as applied to BAT       ●
                     effluent limitations and NSPS for drilling fluids and drill
                     cuttings refers to the bioassay test procedure presented in
                     Appendix 2 of 40 CFR 435, Subpart A.
Bioaccumulation
Potential
                     OECD Guideline for Testing of Chemicals 117 Partition                   ●
                     Coefficient (n-octanol/water) by HPLC 1989.




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               Table 1. Example of survivorship of 5 replicates of 20 animals in 5 concentrations of test
              substance.
              Concentration
                                      Rep 1       Rep 2      Rep 3      Rep 4       Rep 5      Average
              (ppm)

              100,000                    0          0          0             0        0            0

              50,000                     9          7          6             7        8           7.4

              25,000                    10         11          13            9        10         10.6

              12,000                    15         16          18            1        15          16

              0                         20         20          20         20          19         19.8


                   100
                   90
                   80
                   70
Percent Survival




                   60
                   50
                   40
                   30
                   20
                   10
                    0
                         0        20,000          40,000            60,000        80,000          100,000
                                                 Concentration (ppm)

              Figure 1. Relationship of survival and concentration, with arrow indicating lethal
              concentration at which 50% of the population shows mortality (LC50).




                                                                                                        10
                      100.00%

                      90.00%

                      80.00%

                      70.00%
Percent Degradation




                      60.00%

                      50.00%

                      40.00%

                      30.00%
                                                                                     Test Substance 2.23 mpl
                      20.00%
                                                                                     Reference Sodium Benzoate 3 mpl

                      10.00%

                       0.00%
                                0           5             10            15            20                 25                 30
                                                                      Days


                       Figure 2. Aquatic biodegradability of a test substance and reference.




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                   REFERENCES CITED
1. Swift, G., Kirk-Othmer Encyclopedia of Chemical Technology, 4th edition, 19,
   968–1004.

2. ASTM Standards on Environmentally Degradable Plastics, ASTM Publication
   Number (PCN): 03-420093-19.

3. Jirka, A.M., Carter, M.J., Analytical Chemistry, 47(8) 1397 (1975).

4. Federal Register, 26811-26812, 45(78) (April 21, 1980).

5. Lyman, W., Octanol/Water Partition Coefficient, in Handbook of Chemical
   Property Estimation Methods, W.R. Warren Lyman, David Rosenblatt (eds.),
   Washington, D.C., American Chemical Society (1990).

6. C. Hansch, A.J.L., Log P and Parameter Database: A Tool for the Quantitative
   Prediction of Bioactivity, Caremont, California, Pomona College (1982).

7. C. Hansch, A.J.L., Substituent Constants for Correlation Analysis in Chemistry
   and Biology, New York, John Willey (1979).

8. OECD Guideline for the Testing of Chemicals 107 - Partition Coefficient (n-
   octanol/water): Shake Flask Method, OECD (1995).

9. OECD Guideline for the Testing Chemicals 117- Partition Coefficient (n-
   octanol/water), High Performance Liquid Chromatography (HPLC) Method,
   OECD (1989).




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