Test on Degradation of AQUAMUL BII Drill Mud on Cuttings under Simulated Seabed Conditions

Abstract

New, synthetic drilling fluids are exploited by the oil industry to replace mineral oil in muds for North Sea drilling operations. Aquamul BII, which is a modification of the previously tested Aquamul B, is a high purity liquid ether drilling fluid with a stoichiometry corresponding to C20H42O2. In the present study, cuttings contaminated with a mixture of 60% BII and 40% Aquamul B ethers, were tested in benthic chambers at the Solbergstrand Marine Research Station against cuttings contaminated with mineral oil and ester based drilling muds. During the 150 days test period, sediment samples showed significantly decreasing concentrations of all drilling fluids. Estimated halflifes were 20 days for the esters, as compared to more than a year for mineral oil THC and Aquamul ethers. However, enrichment effects were much more prononced in chambers treated with ester cuttings. It was concluded that at the deposition sites in the North Sea the choice between the ester and the ether based muds appeared to be the choice between the ester and ether based muds appeared to be the choice between dramatic effects over a small area of the short period of time and moderate effects over a larger area for a longer period of time.