Munching microbes aid environment, oil industry

January 14, 2002

UH scientist aids EPA on environmental test for synthetic drilling fluids

HOUSTON, - A University of Houston researcher is working with the oil industry and the Environmental Protection Agency to ensure that synthetic-based fluids used to lubricate oil-drilling equipment are environmentally safe.

An EPA ruling published in 2001 says that synthetic-based drilling fluids can be used in drilling operations in the Western Gulf of Mexico if the fluids meet certain guidelines and pass tests indicating they are biodegradable and non-toxic, among other things. The guidelines reduce the discharge of pollutants that have serious environmental impact, including pollutants that kill or impair fish and aquatic organisms, cause health problems through contaminated water, fish or shellfish, and degrade aquatic ecosystems.

EPA guidelines regulate how and how much water-based and petroleum-based fluids can be discharged into the water, but until the 2001ruling there were no specific guidelines covering synthetic-based fluids. Companies must now apply for updated general permits that incorporate the new SBF regulations.

Deborah Roberts, an environmental microbiologist in the civil and environmental engineering department in UH's Cullen College of Engineering, helped develop the biodegradation test cited in the ruling. The EPA and oil industry representatives from the American Petroleum Institute worked together to develop the regulation.

"The EPA ruling establishes restrictions on the discharge of synthetic-based fluids, or SBFs, into the Gulf in order to reduce the potential for adverse environmental impact, while allowing the industry to continue to benefit from their use," Roberts says. "This test determines whether a particular compound will biodegrade sufficiently in the Gulf. Basically, if the microbes in the Gulf sediments eat it, it's OK to use."

On Jan. 8, Roberts presented research about the biodegradation of SBFs in the Gulf at the 21st Information Transfer Meeting in Kenner, La. The Minerals Management Service's Gulf of Mexico Outer Continental Shelf Region sponsored the meeting.

When drilling for oil in the Gulf, drilling operators pump a special mixture of materials, called a drilling mud, down through the drill pipe to cool and lubricate the rapidly rotating pipe and drill bit. The mud carries most of the drilling waste and rock cuttings back up to the surface.

Traditionally, the liquid component of the drilling mud, called the drilling fluid, has been water-based or petroleum-based. Since about 1990, however, the oil and gas extraction industry has developed synthetic-based drilling fluids that enable faster, more efficient drilling and have less of an environmental impact.

Operators try to reclaim as much drilling fluid as they can off the cuttings when they're returned to the surface, Roberts says, but a small percentage of fluid remains on the cuttings, which are usually discharged into the sea. The new regulations identify methods to control the discharge of cuttings associated with SBFs.

"If the industry couldn't use ocean disposal of these cuttings, and instead had to transport them back to shore, it would be more expensive to pump the oil," Roberts says. The EPA estimates that compliance with the rule will result in a reduction of nearly seven million pounds of discharged pollutants a year, and a significant savings in operating costs with no adverse economic impacts to drilling operators. For the EPA's summary on the rule, go to

In 1998, members of the American Petroleum Institute approached Roberts about developing the biodegradation test. Until then, the only tests available for biodegradability were geared toward sewage or for sediments in the North Sea, where conditions are very different from the Gulf of Mexico.

Roberts modified the existing test by using near-shore sediments from the Gulf. The resulting "anaerobic closed bottle test" consists of putting Gulf sediments in a bottle, adding the SBF to be tested, sealing the bottle and incubating the contents.

After 275 days if the sediment's microbes have eaten a certain amount of the SBF, the fluid passes the test. "You know how much of the fluid they've digested by monitoring how much by-product is produced, usually carbon dioxide or methane, depending on the organisms present," Roberts says.

The EPA chose a compound called an internal olefin as the standard compound against which the SBFs are compared. "If your compound degrades within 4 percent of the standard internal olefin, or better, the compound passes," Roberts says. She adds that she has trained workers in private labs to do the test, and those labs will perform the test for a fee.

The next step for Roberts is to gather more data from deep-sea sediments and develop a more accurate model to predict how long it takes various compounds to biodegrade under various environmental conditions. In April and May, the Minerals Management Service plans cruises in the Gulf to gather deep-sea sediment samples.

"It's challenging to gather samples from far offshore in the Gulf where these rigs are operating, and it's hard to do good science when you're at the bottom of the ocean," Roberts explains. "The EPA test is a fair approximation of Gulf conditions, but the goal is to correlate the data from near-shore and deep-sea sediments and develop a clearer picture of what's happening in the deep Gulf."
About the University of Houston

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