Recognising biodegradation in gas/oil accumulations through the δ 13 C compositions of gas components

Pallasser, Robert

doi:10.1016/s0146-6380(00)00101-7

Cited by 203 publications

(110 citation statements)

References 10 publications

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“…The dissolved HCO 3 À discussed in this study had enriched d 13 C values, in the range of þ 17.7% to þ 18.3%. Similarly, isotopically heavy dissolved HCO 3 À has been detected from oil and gas fields, and the primary signature of this HCO 3 À is thought to be the result of anaerobic biodegradation of organic matter through fermentation processes (Carothers and Kharaka, 1980;Pallasser, 2000). These findings suggest that bacterial fermentation of organic matter in groundwater or the deep aquifer matrix leads to production of H 2 and CO 2 , which can serve as the energy and carbon sources for H 2 /CO 2 -using methanogenesis.…”

Section: Discussionmentioning

confidence: 95%

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

et al. 2009

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To identify the methanogenic pathways present in a deep aquifer associated with an accretionary prism in Southwest Japan, a series of geochemical and microbiological studies of natural gas and groundwater derived from a deep aquifer were performed. Stable carbon isotopic analysis of methane in the natural gas and dissolved inorganic carbon (mainly bicarbonate) in groundwater suggested that the methane was derived from both thermogenic and biogenic processes. Archaeal 16S rRNA gene analysis revealed the dominance of H 2 -using methanogens in the groundwater. Furthermore, the high potential of methane production by H 2 -using methanogens was shown in enrichments using groundwater amended with H 2 and CO 2 . Bacterial 16S rRNA gene analysis showed that fermentative bacteria inhabited the deep aquifer. Anaerobic incubations using groundwater amended with organic substrates and bromoethanesulfonate (a methanogen inhibitor) suggested a high potential of H 2 and CO 2 generation by fermentative bacteria. To confirm whether or not methane is produced by a syntrophic consortium of H 2 -producing fermentative bacteria and H 2 -using methanogens, anaerobic incubations using the groundwater amended with organic substrates were performed. Consequently, H 2 accumulation and rapid methane production were observed in these enrichments incubated at 55 and 65 1C. Thus, our results suggested that past and ongoing syntrophic biodegradation of organic compounds by H 2 -producing fermentative bacteria and H 2 -using methanogens, as well as a thermogenic reaction, contributes to the significant methane reserves in the deep aquifer associated with the accretionary prism in Southwest Japan.

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Section: Discussionmentioning

confidence: 95%

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

et al. 2009

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“…5c), δ 13 C-C 2 H 6 values (Table 3; Fig. 5d); δ 13 C-CO 2 values (Table 3), the δ 13 C-CH 4 vs. δ 13 C-CO 2 relationship (Table 3), as well as stable carbon isotope separations between individual pairs of C 1 to C 3 alkanes (Table 3; Clayton, 1998;Milkov, 2005;Pallasser, 2000;Scott et al, 1994;Schoell, 1983;Schoell 1988). Taking all data into account, we conclude that the major fraction of methane originates from microbial formation while a less important methane fraction as well as the majority of higher homologues is provided by thermocatalytic production.…”

Section: Primary Sources Of Lmwhc and Carbon Dioxidementioning

confidence: 99%

“…Admixture of secondary methane, however, appears ambiguous for Batumi seep gases based on our data set. Secondary methane is released by the biodegradation of hydrocarbons and other organic compounds occurring in sediment intervals spanning from deep reservoirs to the surface (Head et al, 2003;Milkov and Dzou, 2007;Pallasser, 2000;Scott et al, 1994;Seewald, 2003) and was assumed to occur in mud volcano deposits in the Sorokin Trough in the Northeastern Black Sea Stadnitskaia et al, 2008).…”

Section: Biological Alterationsmentioning

confidence: 99%

“…These include i) biological degradation of individual compounds (James and Burns, 1984;Kniemeyer et al, 2007;Larter and di Primio, 2005;Pallasser, 2000), ii) preferential incorporation into hydrate cages (Sloan and Koh, 2007), iii) admixture of secondary volatiles derived from degradation of oil (Milkov and Dzou, 2007;Prinzhofer and Pernaton, 1997;Seewald, 2003), and iv) preferential methane consumption mediated by the anaerobic oxidation of methane (AOM) in top sediments (Barnes and Goldberg, 1976;Hinrichs and Boetius, 2002;Hoehler et al, 1994;Reeburgh, 1976). Considering the different alteration effects associated with upward migration and partitioning, the molecular and isotopic composition of LMWHC in shallow sedimentary pools or in vent gas can deviate from the source gas of the reservoir.…”

Section: Introductionmentioning

confidence: 99%

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Molecular and isotopic partitioning of low-molecular-weight hydrocarbons during migration and gas hydrate precipitation in deposits of a high-flux seepage site

et al. 2010

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Detailed knowledge of the extent of post-genetic modifications affecting shallow submarine hydrocarbons fueled from the deep subsurface is fundamental for evaluating source and reservoir properties. We investigated gases from a submarine high-flux seepage site in the anoxic Eastern Black Sea in order to elucidate molecular and isotopic alterations of low-molecular-weight hydrocarbons (LMWHC) associated with upward migration through the sediment and precipitation of shallow gas hydrates. For this, nearsurface sediment pressure cores and free gas venting from the seafloor were collected using autoclave technology at the Batumi seep area at 845 m water depth within the gas hydrate stability zone. Vent gas, gas from pressure core degassing, and from hydrate dissociation were strongly dominated by methane (> 99.85 mol.% of ∑[C 1 -C 4 , CO 2 ]). Molecular ratios of LMWHC (C 1 /[C 2 + C 3 ] > 1000) and stable isotopic compositions of methane (δ 13 C = − 53.5‰ V-PDB; D/H around − 175‰ SMOW) indicated predominant microbial methane formation. C 1 /C 2+ ratios and stable isotopic compositions of LMWHC distinguished three gas types prevailing in the seepage area. Vent gas discharged into bottom waters was depleted in methane by > 0.03 mol.% (∑[C 1 -C 4 , CO 2 ]) relative to the other gas types and the virtual lack of 14 C-CH 4 indicated a negligible input of methane from degradation of fresh organic matter. Of all gas types analyzed, vent gas was least affected by molecular fractionation, thus, its origin from the deep subsurface rather than from decomposing hydrates in near-surface sediments is likely. As a result of the anaerobic oxidation of methane, LMWHC in pressure cores in top sediments included smaller methane fractions [0.03 mol.% ∑(C 1 -C 4 , CO 2 )] than gas released from pressure cores of more deeply buried sediments, where the fraction of methane was maximal due to its preferential incorporation in hydrate lattices. No indications for stable carbon isotopic fractionations of methane during hydrate crystallization from vent gas were found. Enrichments of 14 C-CH 4 (1.4 pMC) in short cores relative to lower abundances (max. 0.6 pMC) in gas from long cores and gas hydrates substantiates recent methanogenesis utilizing modern organic matter deposited in top sediments of this high-flux hydrocarbon seep area.

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“…However, the alteration of marine carbonates is less likely because the host rocks are tuffaceous and rarely contain carbonate minerals, except for the calcic concretions of diapiric blocks and veins. Furthermore, 13 C-enriched CO 2 (δ 13 C > + 5‰) is generated by isotopic fractionation in mud volcanoes by secondary methanogenesis following anaerobic biodegradation of thermogenic hydrocarbons 43,44 . This origin of CO 2 is consistent with the thermogenic character of the gas composition of chibaite.…”

Section: Discussionmentioning

confidence: 99%

New silica clathrate minerals that are isostructural with natural gas hydrates

Momma

Ikeda

Nishikubo³

et al. 2011

Nat Commun

129

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silica clathrate compounds (clathrasils) and clathrate hydrates are structurally analogous because both materials have framework structures with cage-like voids occupied by guest species. The following three structural types of clathrate hydrates are recognized in nature: cubic structure I (sI); cubic structure II (sII); and hexagonal structure H (sH). In contrast, only one naturally occurring silica clathrate mineral, melanophlogite (sI-type framework), has been found to date. Here, we report the discovery of two new silica clathrate minerals that are isostructural with sII and sH hydrates and contain hydrocarbon gases. Geological and mineralogical observations show that these silica clathrate minerals are traces of lowtemperature hydrothermal systems at convergent plate margins, which are the sources of thermogenic natural gas hydrates. Given the widespread occurrence of submarine hydrocarbon seeps, silica clathrate minerals are likely to be found in a wide range of marine sediments.

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Recognising biodegradation in gas/oil accumulations through the δ 13 C compositions of gas components

Cited by 203 publications

References 10 publications

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

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

Molecular and isotopic partitioning of low-molecular-weight hydrocarbons during migration and gas hydrate precipitation in deposits of a high-flux seepage site

New silica clathrate minerals that are isostructural with natural gas hydrates

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