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Degradation of low-toxicity oil-based drilling mud in benthic sediments around the Beatrice Oilfield
Published online by Cambridge University Press: 05 December 2011
Synopsis
Hydrocarbon analyses, using gas-liquid chromatography (GLC), have been conducted on benthic sediments from around the Beatrice A platform immediately after completion of the first well using low-toxicity oil-based drilling mud. These analyses, as expected, showed the major organic contaminant in the sediments to be fresh base oil from the drilling mud. It could be detected to a distance of 3 km from the platform in the direction of the prevailing currents.
A year later, after the completion of five additional wells using low-toxicity oil-based mud, a repeat survey showed the drilling mud base-oil could be detected in similar concentrations (by gravimetry) over the same spatial area. GLC analysis, however, showed that the base-oil had been severely biodegraded at many stations. The degree to which the n-alkanes had been biodegraded varied considerably between stations but appeared to be related to the distance from the platform and/or the total concentration of oil in the sediments. This has resulted in a discrete ring around the platform within which there was a rapid (and in many cases complete) loss of n-alkanes through biodegradation. Possible reasons for this phenomenon are discussed.
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- Copyright © Royal Society of Edinburgh 1986
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