The five-year fate of sea-floor petroleum hydrocarbons from discharged drill cuttings

Abstract

From the Abstract: “An exploratory well was drilled in the North Sea, at a water depth of 60 m, between September 1981 and February 1982, partly with the use of diesel oil-based mud. A total of 200 m3 contaminated cuttings, containing approximately 25 t of oil were released to the sea. After completion of the drilling, the well was capped, and no further drilling activity has taken place in the area since then. To study the fate of the hydrocarbons associated with the cuttings deposited on the sea-floor, samples of the sediment have been collected yearly, the first time 1 month after the discharging was finished, along 4 radial transects at distances between 100 and 3000 m from the well asite. Total petroleum hydrocarbons, as well as selected aliphatics and aromatics were determined. The discharges resulted in an inner heavily polluted area with concentrations of petroleum hydrocarbons between 1000 and >50,000 ug/g (wet weight). The area had an ellipsoidal extension of 500 m in the direction of the wind-driven current during the discharge period. An outer area with concentrations from 1000 ug/g down to the background level of approximately 10 ug/g initially had a longitudinal extension of 2500 m. The change during 5 years were small: no significant decrease in concentrations in the inner heavily polluted area was detected. The extension of the polluted area decreased somewhat during the first year, but remained therafter at approximately 1500 m.”