Genesis of Natural Gas in Marine Carbonate of Sichuan Basin and Bitumen Evidence of TSR Alteration
Received date: 2009-07-01
Revised date: 2009-08-10
Online published: 2009-10-10
Measured the element composition of reservoir bitumen in marine strata of Sichuan basin, and chemical compositions and carbon isotopes of its natural gas, the origin of natural gas could be determined and result in the conclusion that the geochemical origin of natural gas is different from the typical coal\|type gas in China, but similar with the oil-type gas. The thermal maturity of natural gas is generally high, reaching at the stages of that between oil and gas cracking. The partial reverse of the carbon isotopic trend of C1—C3 alkanes is observed, i.e δ13C1>δ13C2<δ13C3. The abnormal phenomena are related to the later thermal sulfate reduction (TSR) to hydrocarbons, for the characteristics of the element composition (i.e. C, H, O, N, S) are different between marine and non\|marine reservoir bitumen. The bitumen in non-marine sand reservoirs in the NE Sichuan basin has low sulfur concentration and low bitumen reflectance; whereas the marine carbonate accumulated bitumen contains high sulfur. The bitumen in marine carbonate was formed by both oil cracking and TSR; in contrast, that in non-marine sandstone was generated from oil cracking.
Key words： Sichuan basin; Marine strata; Gas origin; Solid bitumen; TSR function.
LIU Quan-you,JIN Zhi-jun,WANG Yi,YANG Chun, GAO Bo,ZHANG Dia . Genesis of Natural Gas in Marine Carbonate of Sichuan Basin and Bitumen Evidence of TSR Alteration[J]. Natural Gas Geoscience, 2009 , 20(5) : 759 -762 . DOI: 10.11764/j.issn.1672-1926.2009.05.759
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