Distribution of stable carbon isotope in coalbed methane from the east margin of Ordos Basin

The commercial recovery of methane from coal is well established in the coalbed methane（CBM） blocks at the east margin of Ordos Basin, China. CBM forms with various carbon isotopic ratios（？ 13CPDB） due to the carbon isotopic fractionation in biogenical or thermogenical processes. Based on the geolog...

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Bibliographic Details
Published in:Science China. Earth sciences 2014-08, Vol.57 (8), p.1741-1748
Main Authors: Li, Yong, Tang, DaZhen, Fang, Yi, Xu, Hao, Meng, YanJun
Format: Article
Language:English
Subjects:
Biogas
Carbon isotopes
Coal
Earth and Environmental Science
Earth science
Earth Sciences
Fractionation
Isotope fractionation
Isotopes
Methane
Research Paper
东缘
同位素分布
同位素分馏
定碳
煤层气
甲烷碳同位素
碳同位素比值
鄂尔多斯盆地
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Summary:The commercial recovery of methane from coal is well established in the coalbed methane（CBM） blocks at the east margin of Ordos Basin, China. CBM forms with various carbon isotopic ratios（？ 13CPDB） due to the carbon isotopic fractionation in biogenical or thermogenical processes. Based on the geologic evolution of coalbed reservoir and studies on the characteristics of ？ 13 CPDB values distributed spatially（e.g., horizontal CBM well location area, vertical coal burial zone, coal rank, etc.） and temporally（e.g., geologic evolution history）, we explored the formation mechanism of carbon isotopic of methane. The relatively low ？ 13 CPDB values are widely distributed along the research area, indicating a trend of “lighter-heavier-lighter” from north to south. From a combination analysis of the relationship between ？ 13 CPDB and the relative effects, the essential aspects in determining CBM carbon isotope being light in the study area are： the genesis of secondary biogas in the north; water soluble effects in the active hydrodynamic areas in the middle; desorption fractionation effect promoted by tectonic evolution in the south; and the sudden warming hydrocarbon fractionation accelerated by magmatic event in particular areas（e.g., Linxian）.
ISSN:1674-7313
1869-1897
DOI:10.1007/s11430-014-4900-x