Produced water impact monitoring in the Norwegian sector of the North Sea: Overview of water column surveys in the three major regions

摘要

The Norwegian Pollution Control Authorities (SFT) have since 1999 required environmental monitoring of the water column by the oil companies operating in the Norwegian Sector of the North Sea, in addition to discharge monitoring. Field-based monitoring projects have been conducted in three major production areas to assess the potential impact of produced water discharge; the Tampen, Ekofisk, and Sleipner Regions. The work focuses on contaminants that may bioaccumulate and/or cause toxic effects, including polycyclic aromatic hydrocarbons (PAH) and metals. The fate and effects of the contaminants are determined using field-based techniques and through modeling. The results from the two approaches are used for model validation, and to refine the model and field assessment techniques. The model is also used to develop the Environmental Impact Factor (EIF) for each discharge; the EIF is a risk-based tool used to manage produced water discharges in Norway. Specialized sampling and analytical techniques have been employed to measure contaminants in the sea near and distant to discharges, and to determine potential ecological risk. This has involved deploying caged mussels and semi-permeable membrane devices (SPMDs) at 10-15 sites in each region; mussels and SPMDs concentrate and integrate contaminants in the water, and are used to determine bioaccumulation, critical body burden, and to calculate water-column concentrations. Contaminant concentrations and potential effects have also been determined with dispersion and risk modeling, using discharge data and site-specific environmental information. Results from both approaches to determining contaminant loadings, fate, and potential risk are presented and compared.