Timing of biogenic gas formation in the eastern Qaidam Basin, NW China

Quaternary biogenic gas from the Qaidam Basin, NW China is regarded as one of the representative examples of early generation biogenic gas (gases formed by microbial activity during sedimentation of source rocks). However, new age determinations of natural gas and formation waters make this generall...

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Bibliographic Details
Published in:Chemical geology 2013-08, Vol.352, p.70-80
Main Authors: Zhang, Shuichang, Shuai, Yanhua, Huang, Ling, Wang, Liqun, Su, Jin, Huang, Haiping, Ma, Dade, Li, Maowen
Format: Article
Language:English
Subjects:
Basins
Biogenic gas
Carbon
China
Chlorine-36 dating
Deposition
Formation water
Formations
Freshwater
Methane
Microorganisms
Qaidam Basin
Reservoirs
Stable isotope
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Summary:Quaternary biogenic gas from the Qaidam Basin, NW China is regarded as one of the representative examples of early generation biogenic gas (gases formed by microbial activity during sedimentation of source rocks). However, new age determinations of natural gas and formation waters make this generally accepted assumption questionable. Gas in the Qaidam Basin is dominantly methane (>99.0%), and has δ13CCH4 values in the range of −68‰ to −65‰, reflecting the microbial origin. Carbon and hydrogen isotope values of methane, coupled with carbon isotope values of carbon dioxide and dissolved inorganic carbon (DIC), reflect water derived hydrogen in the methane and a dominant CO2 reduction metabolic pathway for the formation of biogenic methane. Coproduced formation waters have hydrogen and oxygen isotope values similar to surface water from the Golmud and Ortmuren rivers (T-test=0.75), but different from the original formation water (T-test
ISSN:0009-2541
1872-6836
DOI:10.1016/j.chemgeo.2013.06.001