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Marine Water Quality Assessment Of Synthetic-Based Drilling Waste Discharges

Drilling muds or fluids used in drilling operations serve several functions: they lubricate the drill bit; maintain borehole pressure; clean and condition the hole; and flush rock cuttings to the surface. Drilling mud also adheres to rock cuttings, as can formation oil. Barite is used as a weighting agent, which approximately makes up approximately 33% of synthetic mud. It contains traces of heavy metals, which contribute to the toxicity of drilling waste. As environmental issues attract increasing public awareness, the treatment and disposal of spent drilling fluids and contaminated rock cuttings from drilling operations have become sensitive issues for offshore operations around the world. Within the last decade, the oil and gas industry has introduced synthetic-based drilling fluids as substitutes for oil-based fluids. This pollution prevention measure has been complemented by improvements in solid control systems technology. This paper adopts the current U.S. Environmental Protection Agency methodology for a hypothetical case study of an oil field on the East Coast of Canada to determine the water quality impacts of disposal of drilling wastes. The concentration of pollutants at the edge of the mixing zone in the water column and pore water are estimated and compared with Canadian water quality guidelines for protection of aquatic life.