Will Drill Cuttings and Drill Mud Harm Cold Water Corals?

Abstract

Abstract Cold water corals, e.g. Lophelia pertusa and Paragorgia arborea, are found in several places in the Norwegian Sea where oil exploration and production activities are going on. The corals are expected to be vulnerable for sedimentation of particles and exposure to chemicals from drilling activities (drill cuttings and drilling mud) and for physical damage from e.g. anchor lines. How vulnerable they are for these disturbances is, however, not well known. Oil and gas licences licenses in the area are therefore obligated to map possible corals and to take measures to avoid harming them. These obligations have been strengthened in the Integrated Management Plan for the Norwegian Sea approved by the Norwegian Parliament in May 2009. Det norske oljeselskap has in 2009 drilled 4 exploration wells in the Norwegian Sea and carried out a number of activities to map corals, study the effects of drill cuttings and drilling mud, and apply technical and operational measures to reduce the effects. This includes: Mapping of corals around the drill site by use of side scan sonar, multibeam echo sounder and ROV mounted camera/videoMeasurement of particle size distributions in the discharges of cuttings and drilling mudComputer simulation of sea bed currents and sedimentation of discharged particlesAnalyses of particles from sediment traps and sea bottom core samples close to the drill site for verification of simulation models and evaluation of effects on coralsCamera observation of corals before and after the drilling operationRecovery of all cuttings (also from the top hole) to the rig for possible disposal away from corals. Our experience shows that technology is available to handle drill cuttings and mud and control the discharges and spreading to avoid harming corals and other sensitive resources.