Biogenic methane production in formation waters from a large gas field in the North Sea

Abstract

Methanogenesis was investigated in formation waters from a North Sea oil rimmed gas accumulation containing biodegraded oil, which has not been subject to seawater injection. Activity and growth of hydrogenotrophic methanogens was measured but acetoclastic methanogenesis was not detected. Hydrogenotrophic methanogens showed activity between 40 and 80 degrees C with a temperature optimum (ca. 70 degrees C) consistent with in situ reservoir temperatures. They were also active over a broad salinity range, up to and consistent with the high salinity of the waters (90 g l(-1)). These findings suggest the methanogens are indigenous to the reservoir. The conversion of H(2) and CO(2) to CH(4) in methanogenic enrichments was enhanced by the addition of inorganic nutrients and was correlated with cell growth. Addition of yeast extract also stimulated methanogenesis. Archaeal 16S rRNA gene sequences recovered from enrichment cultures were closely related to Methanothermobacter spp. which have been identified in other high-temperature petroleum reservoirs. It has recently been suggested that methanogenic oil degradation may be a major factor in the development of the world's heavy oils and represent a significant and ongoing process in conventional deposits. Although an oil-degrading methanogenic consortium was not enriched from these samples the presence and activity of communities of fermentative bacteria and methanogenic archaea was demonstrated. Stimulation of methanogenesis by addition of nutrients suggests that in situ methanogenic biodegradation of oil could be harnessed to enhance recovery of stranded energy assets from such petroleum systems.

Microbial methane production in deep aquifer associated with the accretionary prism in Southwest Japan

“…Potential for microbial methane production Methane production was observed only in the enrichment amended with H 2 þ CO 2 , similar to earlier observations found in enrichments using formation waters from a gas field in the North Sea (Gray et al, 2009). In Abbreviation: ND, not determined.…”

“…The chemical and isotopic data have been interpreted by plotting hydrocarbon gas composition C 1 /(C 2 þ C 3 ) versus d 13 C-CH 4 (Bernard et al, 1978) and dD-CH 4 versus d 13 C-CH 4 (Schoell, 1983) on widely used conventional diagrams. Numerous microbiological approaches have also been used to understand the methane production processes in subsurface environments such as petroleum-contaminated aquifers (Gray et al, 2009), geothermal aquifers (Kimura et al, 2005;Mochimaru et al, 2007b), and coalbed aquifers (Shimizu et al, 2007;Strąpoć et al, 2008). Igari and Sakata (1989) measured stable carbon isotopic ratios of methane in natural gases associated with the accretionary prism in Southwest Japan, and concluded that the methane was of thermogenic origin.…”

The dominant acetate degradation pathway/methanogenic composition in full-scale anaerobic digesters operating under different ammonia levels

“…The maximum specific growth rate of the mixed methanogenic cultures (l max ) was calculated from the slope of the linear part of the graph of residual methane production (natural logarithm) versus time as described before (Gray et al 2009). …”

Abyssivirga alkaniphila gen. nov., sp. nov., an alkane-degrading, anaerobic bacterium from a deep-sea hydrothermal vent system, and emended descriptions of Natranaerovirga pectinivora and Natranaerovirga hydrolytica

“…Biodegradation thus reduces the gas : oil ratio of the trapped oil, and may result in the exsolution of a dry gas cap enriched in methane and CO 2 (Jones et al, 2008;Larter et al, 2005;Wenger et al, 2002). This process may offer a way to extract energy otherwise trapped in nonextractable oil (Gieg et al, 2008;Gray et al, 2009;Jones et al, 2008). Based on the conversion rates estimated from methane-producing consortia published so far, the commercial potential of the process may be significant (Berdugo-Clavijo & Gieg, 2014;Gieg et al, 2008).…”