27. Application of Quantitative Risk Assessment in Produced Water Management – the Environmental Impact Factor (EIF)

The Dose-related Risk and Effect Assessment Model (DREAM) was developed through a JIP in the period 1997–2000 and was implemented for produced water (PW) management in the Norwegian sector of the North Sea as a part of the ‘Zero discharge work’, 2000–2005. The initial version of DREAM included two approaches to PW management, the Environmental Impact Factor (EIF) and a body burden related risk assessment model focusing on selected PW compounds. The EIF, addressed in the present chapter, has found broad application in the North Sea and has also been used in other offshore production areas by different companies. The produced water EIF is based on the risk assessment principles described in the EU Technical Guidance Document (TGD), comparing the Predicted Environmental Concentration (PEC) and the Predicted No Effect Concentration (PNEC) of PW compounds. The quantitative risk element in the model is represented by the water volume where PEC exceeds PNEC, including the combined risk of all major PW constituents, both naturally occurring compounds and industry-added chemicals. The EIF is used as a management tool, primarily to identify and perform cost–benefit analyses of PW mitigation measures and best available technology (BAT). The method enables the operator to identify the compounds posing the most significant environmental risk in PW, and further to rank different PW discharges with respect to environmental significance and risk. This chapter describes the EIF method and focuses on examples of application of the tool on specific offshore production fields. A description of how the EIF fits into Statoil’s environmental management system is also given, including the link between risk assessment, selection of BAT and field validation through environmental monitoring.