Distribution of suspended particulate drilling wastes at the Hibernia oilfield

From 1995 to 2000, annual surveys were conducted around the Hibernia oil platform off the Grand Banks of Newfoundland. A baseline survey, conducted in 1995 prior to the placement of the offshore platform showed a clean environment devoid of fine particulate matter. Subsequent surveys were conducted to determine the distribution of total suspected particulate drilling fluids in the waters surrounding the gravity base structure. Transects ranging from 0.5 to 20 km from the structure were systematically sampled for water column and benthic boundary later total suspended particulate matter, organic content, disaggregated inorganic grain size (DIGS), optical backscatter, in situ floc size, and high-resolution seafloor imaging. In addition, time series sampling was conducted. Electromagnetic, acoustic and acoustic doppler meters were used to measure the currents in the benthic boundary layer. Samples were analyzed for their particle size spectral characteristics. An algorithm was developed to identify the signature of the bentonite fraction of the disposed drilling fluids. The first survey conducted 4 months after the emplacement of the platform, found particulate drilling wastes in the water column but not in the benthic boundary layer. Subsequent surveys revealed a gradual increase in fine particulate drilling waste in both the water column and the benthic boundary layer, but the overall concentration was low. Most of the material was found within 2 km of the platform. It was concluded that further surveys are warranted given the gradual accumulation of drilling wastes