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- Title
鄂尔多斯盆地奥陶系盐下天然气 地球化学特征及成因.
- Authors
孔庆芬; 张文正; 李剑锋; 昝川莉
- Abstract
The genetic type and source of Ordovician subsalt natural gas in Ordos Basin are discussed so as to provide theoretical basis for gas exploration. Based on the analysis of geochemical characteristics of natural gas, combined with the gas accumulation combination characteristics, the genetic type and source of Ordovician subsalt natural gas are comprehensively identified through the comparison of the stable carbon isotopic compositions of alkane gases and light hydrocarbons and the correlation analysis of δ13C1-RO. The results show that the Ordovician subsalt natural gas in Ordos Basin are mainly composed of hydrocarbon components and the average content is 94. 1%. Methane in hydrocarbon gases is dominant and the methanation parameter(C1/(∑C1-Cn))varies obviously with the difference of regional thermal maturity. From Jingbian to Wushen and Shenmu areas, the methanation parameter gradually decreases from 0.99-0.95-0.85. Except for high sulfur natural gas, the δ13C1 and δ13C2 values of Ordovician subsalt gas are generally low. The δ13C1 value is in ranges from-45.90‰ to -37.29‰, with an average of -39.58‰. The δ13C2 value ranges from -35.58‰ to -25.77‰, with an average of-29.9‰. The carbon isotopic composition of methane and ethane in the high sulfur natural gas under the Ordovician gypsum-salt rock is significantly heavier, which is the result of the thermochemical sulfate reduction(TSR). The results of gas-gas and gas-source correlation of various geochemical index show that the Ordovician subsalt natural gas in Ordos Basin belongs to oil-type gas which is characterized by self-generation and self-accumulation, and the Ordovician marine source rocks are the chief source rocks of producing hydrocarbon.
- Subjects
NATURAL gas prospecting; HYDROCARBON analysis; GYPSUM; CARBON isotopes; REDUCTION of sulfates; NATURAL gas; ANALYTICAL geochemistry
- Publication
Natural Gas Geoscience, 2019, Vol 30, Issue 3, p423
- ISSN
1672-1926
- Publication type
Article
- DOI
10.11764/j.issn.1672-1926.2018.12.020