Degradation of Synthetic-Based Drilling Mud Base Fluids by Gulf of Mexico Sediments Final Report

An important consideration in the environmental assessment of deep-sea drilling operations in the Gulf of Mexico is the discharge of cuttings coated with synthetic-based fluids (SBF). Synthetic-based fluids are one type of nonaqueous drilling fluid and are used in drilling mud to lubricate the drill bit, control reservoir pressure, and bring rock chips, or cuttings, to the surface. Synthetic-based fluids, which can be composed of linear alpha olefins, internal olefins, esters, or paraffins, are released into the marine environment as a residue on the cuttings as they are discharged. This study addressed the fate of the synthetic base fluid portion of the drilling mud in Gulf of Mexico sediments by determining the potential of marine sediment microbes to degrade representative SBF under deep-sea conditions. A model to predict how fast the sediment will recover under realistic conditions was developed to form a scientific basis for evaluating impacts from the discharge of SBF in the deep-sea. This study also examined the effect of the discharge on the microbial ecology of the sediments.