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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

P. J. C. Tibbetts  and
R. Large
P. J. C. Tibbetts
Affiliation:
M-Scan Limited, Silwood Park, Sunninghill, Ascot, Berkshire SL5 7PZ, U.K.
R. Large
Affiliation:
M-Scan Limited, Silwood Park, Sunninghill, Ascot, Berkshire SL5 7PZ, U.K.
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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.

Type
Research Article
Information
Proceedings of the Royal Society of Edinburgh, Section B: Biological Sciences , Volume 91: The Marine Environment of the Moray Firth , 1986 , pp. 349 - 356
Copyright
Copyright © Royal Society of Edinburgh 1986

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References

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