Zero emissions of oil in water from offshore oil and gas installations: economic and environmental implications

‘Produced water’ is seawater mixed with hydrocarbons and derives from the extraction of oil and gas from under the seabed. Its discharge into the marine environment of the North Sea is strictly regulated. This paper discusses the environmental concerns associated with produced water, and the regulatory approach that is currently being taken to reduce produced water discharges into the sea. It is found that there is currently no evidence of harm to the marine environment from produced water, but a number of areas of uncertainty remain. A novel methodology, involving the analysis of material and energy flows, and their associated financial and environmental implications, is used to compare a number of different techniques of reducing these discharges. It is found that these techniques have significant environmental and financial implications. In the absence of evidence of actual environmental harm being caused by produced water, there are three possible precautionary approaches to its management and regulation. The approach that involves zero emissions of produced water implies a relatively high social valuation of the reduction in environmental risk that this achieves.