Biodegradation testing is one of the compliance issues for using Synthetic-Based Drilling Fluid (SBF) technology for drilling oil and gas wells off the US coast. In order to address this issue, the US EPA incorporated a modified version of the standardized biodegradation procedure ISO 11734 as a regulatory limitation for SBF discharges. The test uses marine sediments spiked with the test fluids and incubated anaerobically in closed serum bottles. The production of gas (CO2 and CH4) from the sediment is used to monitor the progress of biodegradation. The source of marine sediment is a critical factor affecting the rate and extent of olefin SBF degradation. This paper describes laboratory studies that investigated the potential of several marine sediments from around the Gulf of Mexico coast to serve as inocula for the anaerobic biodegradation test. Sediment performance was evaluated against chemical, physical, and biological properties in order to identify key screening parameters for selection of sediment in this test. Increasing numbers of sulfate-reducing bacteria, methanogens, general anaerobes, and aerobic hydrocarbon degraders correlated well with increasing degradation rates. The research identified a sediment screening tool that would optimize conditions for fluid degradation and may help avoid costly test-control failures. A study designed to test the effect of sediment storage revealed that sediment could be stored for up to 14 months and still pass the control criteria.

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