BIODEGRADATION OF SYNTHETIC BASE FLUIDS IN GULF OF MEXICO SEDIMENTS

David Herman*
Deborah J. Roberts

University of Houston
Dept. of Civil and Environmental Engineering
Rm N107 Building D
University of Houston
4800 Calhoun
Houston, TX 77204-4003
Voice: 713-743-4283
Fax: 713-743-4260
E-mail: dherman@UH.edu

The oil industry has developed synthetic base fluids (SBF) for use in off-shore oil-drilling operations. SBF are a component of drilling mud needed to lubricate the drill bit and carry rock cuttings to the surface. The environmental impact of SBF in the Gulf of Mexico is of concern due to the discharge of SBF-contaminated rock cuttings onto the sea floor. Determination of the potential of a particular SBF to be biodegraded in marine sediment is required before the SBF is allowed to be used in the Gulf (Federal Registry / Vol. 66, No.111, / Friday, June 8, 2001/Rules and Regulations/30807). The Closed Bottle Test system (Modified ISO 11734) has been chosen as the test system to determine the anaerobic biodegradability of SBF in sediment collected from the Gulf of Mexico. Anaerobic biodegradation of SBF is indicated by the accumulation of anaerobic gases (CO₂ and CH₄) in SBF-spiked sediment, and is verified by determining the removal of SBF from the sediment using GC-FID analysis. Results of Closed Bottle Testing will be presented, along with an evaluation of physical or biological parameters that characterize sediments that supply sufficient microbial inoculum for Closed Bottle Testing. The role of sulfate reducing bacteria in SBF biodegradation was also investigated.