Analysis of Gas Composition and Nitrogen Sources of Shale Gas Reservoir under Strong Tectonic Events: Evidence from the Complex Tectonic Area in the Yangtze Plate

Xin Wang, Zhenxue Jiang, Kun Zhang, Ming Wen, Zixin Xue, Wei Wu, Yizhou Huang, Qianyou Wang, Xiaoxue Liu, Tianlin Liu and Xuelian Xie
Additional contact information
Xin Wang: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
Zhenxue Jiang: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
Kun Zhang: School of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, China
Ming Wen: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
Zixin Xue: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
Wei Wu: Shale Gas Research Institute, PetroChina Southwest Oil & Gas Field Company, Chengdu 610500, China
Yizhou Huang: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
Qianyou Wang: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
Xiaoxue Liu: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
Tianlin Liu: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
Xuelian Xie: Guangzhou Marine Geological Survey, Guangzhou 510760, China

Energies, 2020, vol. 13, issue 1, 1-18

Abstract: Strong tectonic movement brings great risk to exploration of shale gas in southern China, especially in Lower Cambrian shale with complex tectonic backgrounds, which has good hydrocarbon-generation matter but low or no gas content. In this paper, the Lower Cambrian shale from the southeast Chongqing region, located in the Upper Yangtze Platform, and the Xiuwu Basin, located in the Lower Yangtze Platform, were selected as the research objects. First, the gas components in shale gas samples were measured, then analysis of nitrogen isotopic was used to reveal the nitrogen sources. Using regional geological backgrounds, core description, and seismic interpretation, combined with the perpendicular and parallel permeability test and focused ion beam–helium ion microscopy (FIB–HIM) observation, the reasons for high content of nitrogen in the Lower Cambrian shale from the Xiuwu Basin and the Southeast Chongqing region were clarified. The results indicate that the main sources of nitrogen in the Lower Cambrian shale gas at the Southeast Chongqing region is the thermal evolution of organic matter and atmosphere. Nitrogen in the atmosphere is filled into the shale reservoir through migration channels formed by detachment layers at the bottom of the Lower Cambrian, shale stratification planes, and widespread thrust faults. Nitrogen was also produced during the thermal evolution of organic matter. Both are responsible for the low content of hydrocarbon and high content of nitrogen of shale gas in the Southeast Chongqing region. Further, the main sources of nitrogen in the Lower Cambrian shale gas at the Xiuwu Basin is the upper mantle, superdeep crust, and atmosphere. Nitrogen in the atmosphere is also filled into the shale reservoir through migration channels formed by detachment layers at the bottom of the Lower Cambrian, shale stratification planes, and widespread thrust faults. Nitrogen was also produced by volcanism during the Jurassic. Both are the causes of the low content of hydrocarbon and high content of nitrogen in shale gas in the Xiuwu Basin. Finally, destruction models for shale gas reservoirs with complex tectonic backgrounds were summarized. This research aimed to provide a theoretical guidance for shale gas exploration and development in areas with complex tectonic backgrounds.

Keywords: nitrogen isotope; atmospheric source; thermal evolution of organic matter; deep crust-upper mantle source; stratification planes; detachment layers; deep fault; volcanic activity (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: 2020
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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