Dilution and Bioavailability of Produced Water Compounds in the Northern North Sea. A Combined Modeling and Field Study

Abstract

Abstract A combined field and modeling study addressing the dilution and spreading of produced water originating polycyclic aromatic hydrocarbons (PAH) has been carried out in the Tampen region, located in the Norwegian sector of the Northern North Sea. Sampling sites were identified in the region and located in positions near production platforms and in open sea. The station network was designed to cover areas expected to have elevated levels of produced water originating PAH as well as areas not influenced by these discharges, based on dilution modeling of produced water discharge data for the Norwegian and British sectors. Five different sampling techniques were applied in this study. These were deployment of blue mussels and semi-permeable membrane devices (SPMDs) along with direct water sampling for solvent and solid phase extraction and in situ large volume water sampling. Using these results obtained with these techniques, the water concentrations of two selected PAH were compared to regional concentration fields from dilution modeling of produced water discharges from all platforms in the area (Norwegian and British sectors). The results showed that increased levels of PAH in the water phase could be found as far away as 10 km from the nearest discharge source. The agreement between the observed PAH levels and the corresponding levels suggested by the model were very good for the two components included in the present study. As could be expected, the model failed to detect local effects close to the discharge point, when the model was operating on a regional scale.