Oil & Gas Geology ›› 2014, Vol. 35 ›› Issue (1): 159-166.doi: 10.11743/ogg20140121

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Geochemical behaviors of shallow soil in Muli permafrost and their significance as gas hydrate indicators

Xing Xuewen1, Liu Song1, Zhou Hongying1, Zou Liqun1, Li Guangzhi2, Gao Wei2   

  1. 1. PetroChina Research Institute of Petroleum Exploration and Development, Beijing 100083, China;
    2. Hefei Training and Testing Center of Assets Management Ltd. of China Petrochemical Corporation, Hefei, Anhui 230022, China
  • Received:2012-09-03 Revised:2014-01-10 Online:2014-02-08 Published:2014-03-26

Abstract: Muli,the only gas hydrate hosting area in China proved by core sampling,is located in Qilian Mountain permafrost area.Petroleum geochemical exploration was carried out with three hydrocarbon detection techniques(HS,acidolysis hydrocarbon and altered carbonate survey methods)in the area.The results show that the former two methods are more effective than the latter one.Analysis of free hydrocarbons extracted through HS and absorbed hydrocarbons from acidolysis indicates that the components of hydrocarbon gas in soil of areas containing gas hydrate in Muli are complex.In addition to the major component of methane,there are also small amount of ethane,propane,butane and pentane.There are both hydrocarbon gas of pyrolytic origin and that of microbiogenic genesis.The hydrocarbon gas can be classified as oil-prone gas,coal-drived gas and biogas.Methane contrast diagram in combination with the geologic background and core samples in wells discovering gas hydrate reveal that its eastern-central part with well-developed faults and high methane anomaly may be a favorable target for gas hydrate exploration.

Key words: permafrost, soil geochemistry, gas hydrate, Muli area in Qinhai province

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