Oil & Natural Gas Projects
Exploration and Production Technologies
Gulf of Mexico Comprehensive Synthetic-Based Muds Monitoring Program
This project was selected under the Federal Partnership program. The goal was
to cooperate with other Federal government agencies to provide sound environmental
practices to continue oil and gas development in sensitive areas.
The project provided funds to Minerals Management Service (MMS) to allow DOE's
participation in the Gulf of Mexico Comprehensive Synthetic-Based Muds (SBMs)
Monitoring Program. The objective of this study was to assess the fate and physical,
chemical, and biological effects of SBM cuttings discharged from offshore platforms
on the benthic environment of the Gulf of Mexico continental shelf and slope.
Minerals Management Service
Shell Global Solutions
The program performed systematic evaluation of the SBMs by collecting samples
from four cruises in the Gulf of Mexico. Samples were collected and analyzed
for physical, chemical, and biological parameters related to the distribution
of SBM cuttings accumulations on the bottom, as well as the general characteristics
of the benthic communities. There was a sharp decrease in concentrations of
cuttings and chemicals in sediments with distance from the discharge sites,
which indicates that drill cuttings solids, especially from SBM cuttings, are
deposited close to the discharge site. No large, multimeter-thick cuttings piles,
such as those seen in the North Sea, were detected at any of the 15 sites visited
in the study. Discharges were limited to the vicinity of an area 250 meters
from discharge locations.
The review provided input for the development of Effluent Limitation Guidelines
(ELGs), which include technology-based limitations for the discharge of cuttings
generated during drilling with SBMs. Most sediment concentrations of metals
associated with drilling muds were within the range of concentrations for uncontaminated
marine sediments. Evidence was found that indicated that organic enrichment
of discharge sites from physical and chemical disturbances recovered over time.
Significant improvement was observed in the one year between sampling cruises.
In general, sediment quality and biological communities were not severely affected,
and impacts were limited to the vicinity of the discharge (<250 meters).
The need to drill increasingly difficult deepwater and deviated wells, coupled
with the economic and safety advantages of ocean discharge of cleaned cuttings,
has led the offshore oil and gas industry to develop SBMs: drilling muds in
which synthetic materials are the carrier fluid. They are designed to be less
toxic and to degrade faster in marine sediments than oil-based drilling muds,
while providing similar technical advantages in drilling difficult wells.
The U.S. Environmental Protection Agency (EPA) regulates discharges to water
from offshore operations. In 1996, EPA recognized SBMs as a new class of drilling
muds and began reviewing cuttings-treatment technologies and the environmental
impacts of drilling cuttings disposal options. In addition to the requirements
for ELGs, EPA Region 6 general permits requires operators to either conduct
seabed surveys at each location where cuttings drilled with SBMs are discharged
or to participate in a joint-industry seabed survey study.
The research was sponsored by a consortium of companies-the SBM Research Group,
comprised of offshore operators and mud companies-DOE, and MMS.
As of June 1, 2002, the contractor had completed all four sampling cruises.
Initially, 10 sites on the continental shelf were surveyed, and three were chosen
for extensive sampling and analysis. Three locations from the continental slope
also were selected for surveys during the third and fourth cruises. Samples
were collected for analysis of grain size and mineralogy; SBMs and total petroleum
hydrocarbons; metals (aluminum, barium, mercury, and iron); total organic carbon;
and carbonate. Fauna samples and sediment toxicity samples also were collected
and analyzed. During the second cruise, two cores were collected at each of
the 8 sites and vertically sectioned in 1- to 2-cm (or other appropriate) increments.
These sections then were analyzed separately for grain size, metals, and SBMs
to investigate vertical layering. Sediment-profile camera images were collected
in the field and are being analyzed.
Elevated concentrations of barium, a tracer of drilling mud; the synthetic
chemical-based fluid; and total petroleum hydrocarbons were detected in sediments
from the near-field and mid-field zones at the research sites. Most cuttings
were deposited within 100-250 meters of the discharge site on both continental
and continental slope water-depth sites. Based on observations, sediment concentrations
of metals (other than barium) associated with drilling muds were within the
range of concentrations for uncontaminated marine sediments. Metal ratios indicated
that much of the finer-grained sediments near the offshore platforms were from
Measurements of oxygen, total organic carbon, reduction/oxidation potential,
and manganese in sediments-all signs of possible SBM cuttings-related organic
enrichment-indicated that such enrichment occurred near the discharge locations.
Samples collected from multiple survey cruises indicated that the severity of
disturbance in the sediments near the discharge location decreased or the sites
recovered over time.
Sediment toxicity was measured using a non-indigenous, coastal benthic amphipod.
Amphipod survival exceeded 75% in all far-field samples on continental shelf
and continental slope sites, and these sediments were not considered toxic.
At a small number of sites, less than 250 meters from the discharge locations,
amphipod survival was less than 50%, and sediment toxicity and SBM concentrations
were correlated. One-year tests of the sites suggested that the habitat quality
of the sediments had not been seriously degraded by a long history of discharges
at these sites.
The project was completed in 2004, and the final reports were submitted to MMS
Final reports available from NETL at www.netl.doe.gov.
Project Start: June 1, 2000
Project End: August 31, 2004
Anticipated DOE Contribution: $299,946
Performer Contribution: $770,074 (72% of total)
NETL - Rhonda Jacobs (email@example.com or 918-699-2037)
MMS - James Cimato (firstname.lastname@example.org or 703-787-1721)
Collecting mud samples on an offshore rig.
Cleaning and preparing samples for analysis.