Recent Knowledge About Produced Water Composition, and the Contribution from Different Chemicals to Risk of Harmful Environmental Effects

Abstract

Abstract In 1999 the Norwegian Oil Industry Association (OLF) initiated the development of the Environmental Impact Factor (EIF) as a decision making tool for produced water management. The EIF is based on environmental risk and hazard assessment, and makes it possible to identify which of naturally occurring compounds or man-added chemicals contributes most to environmental risk. This possibility leads to increased focus on the quality of results from chemical characterisation of produced water. Data according to the required reporting format given by the Norwegian Pollution Control Authorities (SFT) from the main discharge sources of produced water in the Norwegian sector of the North Sea, have been collected during the period of 1995 to 2000. The data are used as basis for field-specific EIF-calculations. The results show that the most important contributors to environmental risk generally are the water-soluble fraction of the oil; mainly alkylated phenols and polycyclic aromatic hydrocarbons (PAHs). In some cases specific production chemicals also give a significant contribution to the risk of environmental harmful effects. This indicates that the water-soluble fraction of the oil should be focused rather than dispersed oil for most fields as the environmental problem of discharge of produced water. This conclusion emphasises the importance of chemical characterisation, and performing field-spesific evaluations of the risk. This should be reflected both in environmental regulation, and in technology development for reduction of the discharges of environmentally harmful compounds.