首页|Geochemical characteristics,generation,and evolution mechanism of coalbed methane in the south-western Ordos Basin,China

Geochemical characteristics,generation,and evolution mechanism of coalbed methane in the south-western Ordos Basin,China

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The south-western Ordos Basin is rich in low-middle rank coalbed methane(CBM)resources;while the geochemical characteristics and genetic mechanism of CBM are not clear.Herein,according to geological and geochemical test data from gas and coal seam water from CBM wells in Bingchang,Jiaoxun,Huangling,Yonglong,and Longdong minging areas,we systematically studied the geochemical characteristics,generation,and evolution mechanism of CBM in Jurassic Yan'an Formation in the south-western Ordos Basin.The results show that the CH4 content of whole gas is in the range of 42.01％-94.72％.The distribution ranges of the δ13C-CH4 value is-87.2‰to-32.5 ‰,indicating diverse sources of thermogenic gas and biogenic gas.The microbial methane is mainly generated by a CO2 reduction pathway,with certain methyl-type fermentation spots.The δ13C-CH4 has a positive correlation with burial depth,indicating the obvious fractionation of CBM.The relationship between the genetic types and burial depth of the CBM reservoir indicates that the favorable depth of secondary biogenic gas is less than 660 m.The Late Cretaceous Yanshanian Movement led to the uplift of the Ordos Basin,and a large amount of thermogenic gas escaped from the edge of the basin.Since the Paleogene Period,the coal reservoir in the basin margin has received recharge from atmospheric precipitation,which is favorable for the formation of secondary biogenic methane.The deep area,generally under 1000 m,mainly contains residual thermogenic gas.The intermediate transition zone is mixed gas.Constrained by the tectonic background,the genetic types of CBM in different mining areas are controlled by the coupling of burial depth,coal rank,and hydrogeological conditions.The Binchang mining area contains biogenic gas,and the development of CBM has achieved initial success,indicating that similar blocks with biogenic gas formation conditions is key to the efficient development of CBM.The research results provide a scientific basis for searching for favorable exploration areas of CBM in the south-western Ordos Basin.

coalbed methanestable isotopesgeoche-mistrygeneration and evolution mechanismOrdos Basin

Yabing LIN、Yong QIN、Dongmin MA、Shengquan WANG

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College of Geology and Environment,Xi'an University of Science and Technology,Xi'an 710054,China

Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process(the Ministry of Education),China University of Mining and Technology,Xuzhou 221008,China

Shaanxi Provincial Key Laboratory of Geological Support for Coal Green Exploitation,Xi'an 710054,China

National Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaChina Postdoctoral Science FoundationKey Science and Technology Program of Shaanxi ProvinceOpen Fund of Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process of the Ministry of Education(China Univ

42130802423722002022M7137922023YBGY-0832022-007

2024

10.1007/s11707-022-1057-3

地球科学前沿
高等教育出版社

地球科学前沿

CSTPCD
影响因子：0.585
ISSN：2095-0195
年,卷(期)：2024.18(2)
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