The effects of indigenous and introduced microbes on deeply buried hydrocarbon reservoirs, North Sea

Abstract

Anaerobic bacteria were identified in live drilling muds and cores from nine different North Sea and Irish Basin oilfields, varying in depth from 3500 to 15000 ft, and at temperatures up to 150°C. The anaerobic bacteria may be introduced into the reservoir during drilling operations or injection of water, but in many cases the bacteria are indigenous to the oilfield reservoirs. Confirmation of the indigenous anaerobic bacteria was made using molecular biology techniques (16S rDNA sequence analysis), comparing microbial populations present in the blank drilling mud as supplied to wellsite, in the live drilling mud taken during coring, and in the live core. The role of anaerobic bacteria in oilfield diagenesis is not fully understood, though pyrite precipitation, and exopolymer and H2S gas production were noted in this study, up to temperatures of 95°C.

Nannobacterial alteration of pyroxenes in martian meteorite Allan Hills 84001

“…The theoretical arguments draw the lower limit of "life", as we know it, to be 200-250 nm (Knoll and Osborne, 1999). Despite these interesting objections, several laboratories have succeeded in culturing organisms in the 50-100 nm size range, and some have been analyzed to consist ofC, N, a (plus undetectable H), the composition ofliving flesh; TEM has shown cell walls, and they have stained positively for DNA content (e.g., Hiebert, 1994;Kajander and Ciftcioglu, 1998;Vainshtein et a!., 1998;Uwins eta!., 1998Uwins eta!., , 1999Prabhakaran, 1999;Gillet etal., 2000;Spark et al, 2000;Folk and Taylor, 2000;Folk et al, 2001a).…”

Anaerobic Biodegradation of Aromatic Hydrocarbons: Pathways and Prospects

“…This potential would be increased by discovery of new electricigens with innate hydrocarbon-degrading abilities, or by genetic engineering of known electricigens to introduce the appropriate anaerobic catabolic genes, once available. Head et al [2003] have reviewed the literature on deep subsurface oil reservoirs and support the proposition that heavy oils have arisen through anaerobic biodegradation of conventional oils over geologic time, occurring in reservoirs with a water interface and an in situ temperature ^ 80 ° C [Aitken et al, 2004;Larter et al, 2006;Röling et al, 2003] or perhaps higher [Spark et al, 2000]. Deep subsurface biodegradation, involving aliphatic as well as aromatic hydrocarbons, is generally deleterious to the economic value of the oil, resulting in increased oil density and viscosity, sulfur content, acidity and metals, and decreased saturated and aromatic hydrocarbons corresponding to the extent of in situ biodegradation [Larter et al, 2006].…”

Use of Microbial DNA Probes as a Potential New Tool in Oil Exploration and Characterization

“…Microbial growth in oil reservoirs has traditionally been associated with fouling problems caused by sulphate-reducing bacteria (SRB), or biomass-generated near-well plugging. Several thermophilic sulphate reducers have been isolated from hot oil reservoirs by culture techniques 2,12,14,16,18,9 . It is known that microbes may grow at temperatures well above 100°C under pressure 10 , and the limits for growth and survival are probably related to water vapour pressure rather than to temperature.…”