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Questions, Answers, and Related Resources
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BP's Thunderhorse platform, Gulf of
Mexico |
1. What kinds of waste materials
can be produced during offshore oil and gas exploration or production
activities?
The bulk of waste materials produced by offshore oil and gas
activities are formation water (produced water) and drilling muds and cuttings.
Additional waste materials include small
quantities of treated domestic and sanitary waste, deck drainage, once-through
fire water, non-contact cooling water, bilge water, ballast water, produced
sands, waste oil, excess cement, chemical products, and trash and debris.
All of these waste streams are regulated by the
U.S. Environmental Protection Agency (EPA) through discharge permits and are
either released after treatment or returned to shore for disposal.
2. Which wastes generated from
offshore oil and gas exploration and production activities may be discharged
into the ocean?
Routine discharges may include water-based drilling muds and
cuttings, synthetic-based mud cuttings, treated produced water, treated sanitary
and domestic waste, deck drainage, once-through fire water, and non-contact
cooling water. Other wastes, such as excess
cement and bilge and ballast waters, may be discharged at some point in the
operation. All discharges are regulated by the
EPA.
The EPA prohibits the discharge of some wastes.
These include oil-based drilling muds and
cuttings, produced sands, synthetic-based muds, waste oil, chemical products,
and trash and debris, none of which can be discharged into the ocean.
3. What are the alternatives to
discharging offshore oil and gas exploration and production wastes into the
ocean?
The wastes may be reinjected into geologic formations (i.e.,
layers of rocks sharing common properties) or disposed of onshore.
Wastes that do not meet regulatory requirements
for offshore discharge into the ocean must be properly disposed of or recycled
onshore according to state and federal regulations.
4. What agencies and regulations
govern the routine discharge of wastes produced by offshore oil and gas
exploration and production activities?
Routine discharges of wastes are subject to regulation by the
EPA under Section 402(a) of the Clean Water Act (CWA). The
EPA, a regulatory agency, is authorized by Congress to implement pollution
control programs and to write and enforce regulations necessary to implement
environmental laws, such as the CWA.
The EPA establishes effluent limitation guidelines through a
rigorous process to evaluate potential impacts, solicit public review and
comment, and set restrictions on the volume and composition of discharges to
comply with applicable water quality standards, which are then incorporated into
the National Pollutant Discharge Elimination System (NPDES) permitting process.
In 1993, the EPA established guidelines for the discharge of
offshore drilling and operational wastes. NPDES
permits contain effluent limitations (developed pursuant to a number of sections
of the CWA including 301, 302, 306, 307, and 403) and operating conditions which
depend on the permit region. Operators must
apply to the EPA for permit coverage to discharge drilling and production wastes
to the Outer Continental Shelf (OCS) before the Mineral Management Service (MMS) authorizes activities.
The MMS shares in regulating offshore discharges to the ocean.
The MMS may require lessees and operators to
further regulate effluent discharges by imposing "mitigating measures" on
certain operations. Through these measures, the
MMS could require operators to (1) conduct a bottom survey to locate sensitive
features or areas, (2) relocate operations to avoid sensitive areas, (3) shunt
drilling fluids and cuttings to the ocean bottom, thus decreasing the time these
materials are suspended in the water column, (4) monitor activities to assess
the adequacy of mitigating measures, and (5) regulate discharge rates.
Before a company begins drilling or production activities, the
MMS evaluates and approves each plan. The MMS
also routinely inspects offshore facilities to ensure that permit requirements
are being met.
5. What are drilling muds?
During the drilling of a well, drilling fluids or "muds" are
used to lubricate and cool the drill bit, control reservoir pressure, and
transport the drill cuttings back to the surface. Drilling
discharges are made up of drilling muds that have not stayed in the borehole and
cuttings, the crushed rock from the borehole.
Three general types of drilling muds have been used during
drilling operations: water-based drilling muds,
oil-based drilling muds, and synthetic-based drilling muds.
Water-based drilling fluids or muds (WBF or WBM) are used at
some stage during all well drilling. The primary
components of WBM are fresh or salt water, barite, clay, caustic soda, lignite,
lignosulfonates, and water soluble polymers. The
specific composition depends on the type of formation (i.e., layers of rocks
sharing common properties) being drilled. WBM
and WBM-wetted cuttings may be discharged.
Oil-based drilling fluids or muds (OBF or OBM)
are used to improve drilling through difficult formations.
The base mud for OBM is typically diesel or
mineral oil. Because these oils often contain
toxic materials such as polynuclear aromatic hydrocarbons (PAHs), the discharge
of OBM or cuttings wetted with OBM is prohibited.
Synthetic-based drilling fluids or muds (SBF or SBM) were
developed as an alternative to OBM when drilling activities began moving into
deeper waters. The base fluid is a synthetic
material, typically an olefin or ester, free of toxic PAHs. Discharge
of SBM is prohibited. However, SBM-wetted
cuttings may be discharged after the majority of the SBM has been removed.
Drilling muds are regulated by the EPA and can be discharged
into the ocean only if they meet EPA requirements, which include testing for
toxicity prior to discharge. If they fail the
toxicity tests, the materials cannot be discharged to the ocean.
The discharges cannot exceed set discharge
rates.
6. What is produced water?
Produced water is mainly salty water trapped in the reservoir
rock and brought up with oil or gas during production. It
can contain very minor amounts of chemicals added downhole during production.
These waters, which are under high pressures and
temperatures, must be treated, because they usually contain oil and metals.
Before being discharged, produced water must
meet established limitations on oil content. As
with drilling muds, following treatment, produced water must be tested for
toxicity, according to EPA requirements. If it
fails the toxicity test, it cannot be discharged into the ocean.
When discharge into the ocean is permitted, the
discharge cannot exceed set discharge rates.
7. Has research been done to
determine the effects of these discharges on the marine environment?
Yes. Offshore drilling and
production discharges and their environmental effects have been studied for over
30 years. In 1973, the MMS (then the Bureau of
Land Management) began its Environmental Studies Program to investigate
potential effects of oil and gas production activities on the marine
environment.
Key concerns include the fate of the discharges in the
environment, including dispersion, degradation, and deposition resulting in
smothering and alteration of the seafloor environment. Also
of concern are acute and chronic toxic effects on plant and animal life both in
the water column and at the ocean floor.
In general, study results indicate that the observable effects
are limited to radial distance of 100 to 1,000 meters from the discharge point;
the area is greater in deep waters. Assuming
that mitigation measures are implemented, acute responses to drilling discharges
are unlikely.
The primary mitigation measures include: (1)
prohibition on the discharge of muds and cuttings containing OBM; (2)
prohibition on the discharge of SBM and limits on the concentration of SBM on
discharged cuttings; and (3) the dispersion of WBM and cuttings, unless the
discharge radius is in close proximity to a sensitive biological community.
MMS-sponsored studies are available to the public.
Reports from the Environmental Studies Program
may be searched and downloaded at:
https://www.gomr.mms.gov/homepg/espis/espismaster.asp?appid=1
Alternatively, studies for the Gulf of Mexico OCS Region are
listed by year at:
http://www.gomr.mms.gov/homepg/regulate/environ/techsumm/rec_pubs.html.
Related Links
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