文章基本信息

标题：Subsurface biodegradation of crude oil in a fractured basement reservoir, Shropshire, UK
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作者：John Parnell ; Mas'ud Baba ; Stephen Bowden 等
期刊名称：Journal of the Geological Society
印刷版ISSN：0016-7649
电子版ISSN：2041-479X
出版年度：2017
卷号：174
期号：4
页码：655-666
DOI：10.1144/jgs2016-129
语种：English
出版社：Geological Society Publishing House
摘要：Subsurface biodegradation of crude oil in current oil reservoirs is well established, but there are few examples of ancient subsurface degradation. Biomarker compositions of viscous and solid oil residues (‘bitumen’) in fractured Precambrian and other basement rocks below the Carboniferous cover in Shropshire, UK, show that they are variably biodegraded. High levels of 25-norhopanes imply that degradation occurred in the subsurface. Lower levels of 25-norhopanes occur in active seepages. Liquid oil trapped in fluid inclusions in mineral veins in the fractured basement confirms that the oil was emplaced fresh before subsurface degradation. A Triassic age for the veins implies a 200 myr history of hydrocarbon migration in the basement rocks. The data record microbial biodegradation of hydrocarbons in a fractured basement reservoir, and add to evidence in modern basement aquifers for microbial activity in deep fracture systems. Buried basement highs may be especially favourable to colonization, through channelling fluid flow to shallow depths and relatively low temperatures, and are therefore an important habitat within the deep biosphere.