Effects of Chemicals Used in Oil and Gas Well-Drilling Operations in Aquatic Environments - DRAFT

Increased exploratory and developmental oil and gas drilling offshore and in the Great Lakes has heightened concern over potential adverse environmental effects of such activities. The U.S. Environmental Protection Agency, National Oceanic and Atmospheric Administration, Bureau of Land Management, U.S. Geological Survey, and various state agencies have legislative mandates related to various phases of oil and gas exploration and development. E.P.A. drilling-related research and monitoring programs parallel the Agency's mission under the Federal Water Pollution Control Act to regulate discharges into open waters. E.P.A. Regional Offices have authority to issue waste discharge permits and to specify conditions for permits. Environmental concerns include effects of chemicals discharged during oil and gas drilling activities that originate from: (a) "drilling fluids" or "drilling muds" -- chemicals added to the well-bore; later discharged; (b) "cuttings" -- formation solids that become suspended in the drilling fluid; and (c) formation water and its dissolved, emulsified and suspended solids. These effluents are discharged into the aquatic environment during exploratory and development drilling. This paper summarizes objectives of research designed to assess the potential hazard to the aquatic environment and man from drilling practices, and to evaluate mitigating options. Oil and gas drilling hazard assessment is based on a blending of results from research on (a) exposure assessment and (b) effects assessment. Exposure assessment is determined by the chemical analysis of drilling fluids and components, chemical fate studies, field studies of drilling rigs and platforms, and discharge plume modeling. Effects assessment is accomplished through a stepped sequence of toxicity tests that includes both laboratory and field toxicity testing of drilling fluids and their components. Hazard assessment is region-specific and includes considerations of environmental concentrations of drilling fluids likely to have commercial, recreational, aesthetic, or ecological significance. Hazard assessment must be developed region by region because of community and habitat uniqueness. For example, the New England coast has commercially important cold water fisheries in a high-energy hydrographic regime, "Georges Bank"; the northwestern Gulf of Mexico has petroleum hydrocarbon reserves and coral reefs, the "Texas Flower Garden Bank"; Lake Erie is undergoing restoration and may have gas reserves. Hazard assessment in diverse geographical areas is essential to sound evaluations of candidate alternative chemicals for use in well-drilling operations. Furthermore, the impact of alternate operational procedures can be evaluated on the basis of hazard assessment tradeoffs. Hard data on environmental concentrations and toxicological effects of drilling fluids may help eliminate unjustified concern about certain chemicals used in drilling fluids which may be safely used in well-drilling operations. It may also prevent over-and under-regulation of offshore oil and gas resource development and production.