Gas geochemistry characteristic of shale gas in Longmaxi Formation, SE Sichuan Basin, China

Shale gas samples collected from Lower Silurian Longmaxi Formation of Southern Sichuan Basin in Weiyuan were analysed for stable isotope composition of noble gases and molecular composition, stable carbon isotope composition of hydrocarbons. Results show these shale gases are of organic origin gas,...

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Bibliographic Details
Published in:IOP conference series. Earth and environmental science 2017-01, Vol.52 (1), p.12009
Main Authors: Cao, Chunhui, Du, Li, Li, Liwu, He, Jian, Li, Zhongping
Format: Article
Language:English
Subjects:
Carbon dioxide
Carbon isotopes
Carbonates
Chemical composition
Gas sampling
Gases
Geochemistry
Helium
Hydrocarbons
Isotope composition
Isotopes
Organic matter
Rare gases
Shale
Shale gas
Shales
Silurian
Stable isotopes
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Summary:Shale gas samples collected from Lower Silurian Longmaxi Formation of Southern Sichuan Basin in Weiyuan were analysed for stable isotope composition of noble gases and molecular composition, stable carbon isotope composition of hydrocarbons. Results show these shale gases are of organic origin gas, and produced at high-over maturity stage. All the analysed hydrocarbon gases reveal complete inversed isotopic trends from methane to propane, and δ13C1, δ13C2 have obviously different between Weiyuan and Changning areas. CO2 was mainly generated during thermogenic processes of transformation of organic matter, although some gases can contain components from endogenic processes and from thermal destruction of carbonates. He and Ar are mainly product of α-decay of U and Th enriched in crustal materials. A small contribution of mantle origin He was found in the gas reservoirs. Continuous monitoring data indicate 3He/4He ratio didn't change with the mining time.
ISSN:1755-1307
1755-1315
DOI:10.1088/1742-6596/52/1/012009