Chemical, carbon and sulfur isotopic compositions constrain the origin of Upper Carboniferous-Lower Triassic gases in eastern Sichuan Basin, SW China

Methane dominated gas is one of the cleanest energy resources; however, there is no direct method to determine its source rock. Natural gases produced from the eastern Sichuan Basin together with seismic data were studied for their sources and secondary alteration by thermochemical sulfate reduction...

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Bibliographic Details
Published in:Science China. Earth sciences 2024-10, Vol.67 (10), p.3169-3185
Main Authors: Cai, Chunfang, Kutuzov, Ilya, Mei, Wenhua, Wang, Daowei, Luo, Bing, Huang, Shipeng, He, Bing, Amrani, Alon
Format: Article
Language:English
Subjects:
Carboniferous
Chemical composition
Earth and Environmental Science
Earth Sciences
Energy resources
Energy sources
Gases
Geochemistry
Hydrogen sulfide
Isotope composition
Methane
Natural gas
Organosulfur compounds
Permian
Rock
Rocks
Seismic data
Seismological data
Silurian
Sulfate reduction
Sulfates
Sulfur
Sulfur compounds
Sulphate reduction
Sulphur
Sulphur compounds
Triassic
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Summary:Methane dominated gas is one of the cleanest energy resources; however, there is no direct method to determine its source rock. Natural gases produced from the eastern Sichuan Basin together with seismic data were studied for their sources and secondary alteration by thermochemical sulfate reduction (TSR). Our results demonstrate that Upper Permian to Lower Triassic (P 3 ch-T 1 f) gases in the surrounding of the Kaijiang-Liangping area show volatile organic sulfur compounds (VOSCs) δ 34 S values close to those of the associated H 2 S, and may have been altered by methane-dominated TSR, resulting in positive shift in methane δ 13 C 1 values with increasing TSR extents. Other (or group 2) gases produced from the P 3 ch-T 1 f reservoirs from the southern area and the Upper Carboniferous to Middle Permian (C 2 h-P 2 q) from the eastern Sichuan Basin are not significantly changed by TSR, show similar δ 34 S values between the kerogens and some VOSCs, and may have been derived from the Lower Silurian and Middle Permian source rocks. This study demonstrates a case for the first time showing the δ 34 S values of VOSCs can be used as a tool for direct correlation between non-TSR altered gas and source rocks. Methane-dominated gas pools can be found using gas and source rock geochemistry combined with seismic data.
ISSN:1674-7313
1869-1897
DOI:10.1007/s11430-024-1368-0