Parameterisation of the Environmental Impacts on Bottom Fauna of Water-based Drilling Fluids and Cuttings

Discharges of contaminated drill-cuttings have caused appreciable ecological changes in the bottom fauna around many Norwegian oil and gas platforms. Drilling-induced disturbances reduce the diversity and complexity of pristine bottom fauna and restricts their functions. The effects may be due to physical disturbance (sedimentation and smothering), chemical toxicity or heavy organic loading (and subsequent oxygen problems in the sediments). In order to aid the prediction and evaluation of harmful biologic al effects and the environmental risk of using various chemicals in the Norwegian offshore drilling activities, modelling has been introduced as an important tool. The models have till now mainly been applied for processes in the water column, but recentl y transport of sediments and chemicals to the seabed has been included in the modelling work. The seabed part of the model has till now been based on physical/chemical processes, without incorporating the impacts of the bottom-dwellin. We will also quanti tatively describe biological effects of drilling discharges on the bottom fauna. This project aims to provide important information needed to better evaluate and predict risk of effects of drill-cuttings disposal and also predict the restitution time need ed for a new bottom-dwelling fauna to establish on seabed receiving larger amounts of drilling discharges.