Effect of Volcanic Events on Hydrocarbon Generation of Lacustrine Organic-Rich Shale: An Example of the Upper Triassic Galedesi Formation in the Hala Lake Depression, South Qilian Basin, China

Jia Wang, Chaobin Zhu, Xianfeng Tan, Long Luo, Nan Jiang, Xuejiao Qu, Xuanbo Gao, Shengyu Li, Long Xiao and Haijun Liu
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Jia Wang: Chongqing Key Laboratory of Complex Oil and Gas Exploration and Development, Chongqing University of Science & Technology, Chongqing 401331, China
Chaobin Zhu: Chongqing Key Laboratory of Complex Oil and Gas Exploration and Development, Chongqing University of Science & Technology, Chongqing 401331, China
Xianfeng Tan: Chongqing Key Laboratory of Complex Oil and Gas Exploration and Development, Chongqing University of Science & Technology, Chongqing 401331, China
Long Luo: Chongqing Key Laboratory of Complex Oil and Gas Exploration and Development, Chongqing University of Science & Technology, Chongqing 401331, China
Nan Jiang: Chongqing Key Laboratory of Complex Oil and Gas Exploration and Development, Chongqing University of Science & Technology, Chongqing 401331, China
Xuejiao Qu: Chongqing Key Laboratory of Complex Oil and Gas Exploration and Development, Chongqing University of Science & Technology, Chongqing 401331, China
Xuanbo Gao: Chongqing Key Laboratory of Complex Oil and Gas Exploration and Development, Chongqing University of Science & Technology, Chongqing 401331, China
Shengyu Li: Chongqing Key Laboratory of Complex Oil and Gas Exploration and Development, Chongqing University of Science & Technology, Chongqing 401331, China
Long Xiao: Qinghai Coal Geological Exploration Institute, Xining 810008, China
Haijun Liu: China Southwest Geotechnical Investigation & Design Institute Co., Ltd., Chengdu 610052, China

Energies, 2022, vol. 15, issue 10, 1-12

Abstract: The thermal evolution process of organic matter is associated with the complete hydrocarbon generation and expulsion process in shale, however, the thermal evolution of organic matter is a long process and cannot be realized without experimental simulations. Although several scholars have substantially studied the thermal evolution of organic matter, it remains a challenging and much debated issue in the studies of organic geochemistry. Volcanic events are crucial in the enrichment of organic matter, and appropriate heating accelerates the thermal evolution of organic matter. However, how strong-rock baking restricts the evolution of organic matter in shale has not been specifically studied. The South Qilian Basin in China is a typical superimposed basin where complex tectonic movements have induced multiple volcanic events, which makes it a favorable location to perform the aforementioned research. This study used the Galedesi Formation shale in the Hala Lake Depression of the South Qilian Basin as an example for investigating the constraints of the volcanic events related to the thermal evolution of organic matter by integrating the results obtained using the geochemical and petrological methods. Our results demonstrate that the lacustrine Galedesi Formation shale of the Hala Lake Depression in the Late Triassic is a typical deep-lake facies deposit with good hydrocarbon generation potential. However, because of the influence of regional tectonic evolution, the burial depth of shale is not deep and the thermal evolution of organic matter is insufficient. Due to the influence of multiple volcanic thermal events in the later stages, the thermal maturity of organic matter in the Galedesi Formation shale generally exceeds 3.0%, which is abnormally high. The apparent carbonization of organic matter can be observed via scanning electron microscopy. Rapid magma baking typically cannot effectively promote the hydrocarbon generation of shale organic matter. Finally, the burial depth of lacustrine shale of the Galedesi Formation in the Hala Lake Depression of South Qilian Basin is too shallow. Organic matter hydrocarbon generation and later shale preservation conditions are not conducive to the enrichment, accumulation, exploration, and development of shale gas.

Keywords: organic matter; thermal evolution; shale; Galedesi Formation; South Qilian Basin (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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