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- Title
Evaluation of source rocks in the 5<sup>th</sup> member of the Upper Triassic Xujiahe Formation in the Xinchang Gasfield, the Western Sichuan Depression, Sichuan Basin.
- Authors
Wu Xiao-qi; Chen Ying-bin; Zhao Guo-wei; Du Xiao-wei; Zeng Hua-sheng; Wang Ping; Wang Yan-qing; Hu Ye
- Abstract
The 5th member of the Upper Triassic Xujiahe Formation (T3x5) is one of the important targets for terrigenous natural gas exploration in the Xinchang Gasfield in the Western Sichuan Depression, however, the quality of the T3x5 source rocks is poorly studied and the understanding of it is controversial. Studies have been conducted on the development and organic geochemical characteristics of the T3x5 mudstone in the Xinchang Gasfield,and the results indicate that,the T3x5 mudstone in the Xinchang Gasfield display an average thickness of 285.3m, and the thickness of each submember increases from north to south. The average TOC content, hydrocarbon potential (S1+S2) and chloroform bitumen “A” content of T3x5 mudstone are 2.17 %, 2.26mg/g and 0.264‰, respectively, with the organic abundance mainly reaching the standard of medium source rocks.The kerogen type index (TI) is lower than 0 with the mean S13C value of -25.0‰ indicating mainly humic and sapropelic-humic types of organic matters. The average vitrinite reflectance (RO) value is 1. 1 7 %, indicating the stage after the peak of oil generation. The gas generation intensity of T3x5 mudstone is generally in the range of (3-16) X 108m3/km2, which suggests the resource basis for the generation of medium-small gas fields. The total amount of natural gas generated by T3x5 mudstone in the Xinchang Gasfield is relatively low, and the generated gas cannot completely displace the water in the formation, therefore, the fullness of gas in the reservoirs is generally low, which causes the simultaneous production of gas and water and the low gas production in the process of production test.
- Subjects
XUJIAHE Formation (China); NATURAL gas prospecting; NATURAL gas production; ANALYTICAL geochemistry; SAPROPELITES; TRIASSIC stratigraphic geology
- Publication
Natural Gas Geoscience, 2017, Vol 28, Issue 11, p1
- ISSN
1672-1926
- Publication type
Article
- DOI
10.11764/j.issn.1672-1926.2017.07.003