Toril Inga Røe Utvik

Determining produced water originating polycyclic aromatic hydrocarbons in North Sea waters : Comparison of sampling techniques

Abstract A field study was carried out in the Norwegian sector of the North Sea during May and June 1997. The purpose was to measure the concentration of produced water originating polycyclic aromatic hydrocarbons (PAH) in seawater and to compare different sampling techniques for use in future monitoring programs. Three methods were used for direct water sampling: (1) in situ large volume sampling of particulate and dissolved hydrocarbons onto filters and XAD resins, (2) solid phase extraction (SPE) using polystyrene-divinylbenzene disks, (3) whole bulk water sampling. In addition, sampling by semi-permeable membrane devices (SPMDs) and blue mussels (Mytilus edulis) was used to obtain a 4 weeks average of the concentration of the target compounds in seawater. The samples were processed and analysed by GC–MS for determination of PAH concentrations. The measured concentrations were generally found to be low, and in many cases below the limits of detection. The comparison of sampling techniques showed that blue mussels and SPMDs are suitable for measuring PAH in both near- and far-field seawater. In situ large volume water sampling was also suitable for a wide range of PAH concentrations, but this technique was limited by high break-through of the low-molecular weight compounds, such as naphthalenes. The small sampling volumes limited the SPE and whole water sampling techniques, resulting in potential detection limit problems. These grab-sampling techniques may, however, be suitable for monitoring in the near-field areas around the platforms.

Comparison of the ParTrack mud/cuttings release model with field data based on use of synthetic-based drilling fluids

A model for the calculation of the spreading and deposition of drilling mud and cuttings has been developed. The calculations are based on a Lagrangian particle approach, which means that the properties of the discharge are represented by moving particles in the model domain. The initialization of the particles is based on the output from an Eulerian near-field underwater plume model. In addition, the model applies external current fields for the horizontal advection of the particles. The paper explains details in a comparison made between measured barium concentrations in the sediment and the modeled deposition on the sea floor from the drilling of eight exploration wells and eight production wells for the development of an oil field in the North Sea.

Comparison of the ParTrack mud/cuttings release model with field data

Abstract The oil industry promotes the development of numerical models for prediction of impacts from their discharges to sea. A model for the simulation of the spreading and deposition of drilling mud and cuttings on the sea floor as well as the spreading of chemicals (and small-sized particles) in the water column has been developed. The simulation is based on a Lagrangian ‘particle’ approach, which means that the properties of the discharge are represented by moving ‘particles’ in the model domain. The initialization of the particles is based on the output from an Eulerian near field underwater plume model. In addition, the model applies external current fields for the horizontal advection of the particles. This paper presents a comparison between simulated and measured concentrations of barium (barite) in surface contaminated sediment in the vicinity of an oil production field. As a part of the regular surveillance of oil production sites on the Norwegian Continental Shelf, the barium content in surface sediments is measured. These data might therefore serve as an opportunity for comparing simulation results with measured depositions of barium (barite) on the sea floor. The paper explains details in the comparison made between the measured barium concentrations in the sediment and the simulated deposition on the sea floor from the drilling of three exploration wells and 18 production wells off the west coast of Norway.