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Depositional Environment of Coal and Oil Shale of Middle Jurassic Shimengou Formation in Tuanyushan Area, Qaidam Basin(PDF)


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Depositional Environment of Coal and Oil Shale of Middle Jurassic Shimengou Formation in Tuanyushan Area, Qaidam Basin
CHEN Lingling12 MENG Qingtao12 LIU Zhaojun12 XU Yinbo3 SUN Pingchang12 WANG Kebing12
(1.School of Earth Sciences, Jilin University, Changchun, Jilin 130061, China; 2.Jilin Key Laboratory for Oil Shale and Paragenetic Energy Minerals, Changchun, Jilin 130061, China; 3.Oil and Gas Resource Survey Center, China Geological Survey, Beijing 100083, China)
Qaidam basin Tuanyushan area Middle Jurassic Shimengou formation oil shale coal organic geochemistry water environment
The Middle Jurassic coal and oil shale are widely developed in the Tuanyushan area in the northern margin of the Qaidam basin, but the exploration level in the area is relatively low and the researches on the depositional environment and genesis of the coal and oil shale are relatively weak. Therefore, the paper uses the QD-2 full cored well in Tuanyushan area to study the organic geochemical characteristics and depositional environments of the coal and oil shale in the study area based on the analysis on rock pyrolysis, total organic carbon, industrial quality parameter, gas chromatography and gas chromatography-mass spectrum. The study shows that the oil shale is characterized by high ash content, low organic carbon content and low-medium oil-bearing rate, and the coal belongs to low ash content, high organic carbon content and low metamorphic grade lignite. N-alkanes, isoprenoid, terpenoid, steroid and aromatic hydrocarbons are detected in the coal and oil shale. On the gas chromatography, N-alkanes in both coal and oil shale are in single-peak distributions with the first lower and later higher shape. The Pr/Ph value of coal is higher than that of oil shale, the relative content of the regular sterane is C29>>C28>C27, abundant sesquiterpenoids and diterpenoids are detected in aromatic compounds. The comprehensive analysis shows that the coal and oil shale are at the immature stage of evolution and the organic matter mainly comes from terrestrial gymnosperms. The oil shale formed in a weak oxidation, fresh water and shallow lake environment and the coal formed in an oxidizing marsh environment. Therefore, as for the source of organic matters, there are no significant differences between the coal and oil shale, but their sedimentary environments are largely different. The comparison shows that the differences existed in the organic matter type, source and sedimentary environment result in the different occurrence characteristics of the oil shales in the coal-bearing intervals and in the shale intervals in the Shimengou formation of Tuanyushan area in Qaidam basin




Last Update: 2018-12-05