Oil & Gas Geology ›› 2018, Vol. 39 ›› Issue (1): 54-65.doi: 10.11743/ogg20180106

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Paleo-structure features in the 1st member of the Upper Paleozoic Shanxi Formation and its influences on gas accumulation in southwestern Ordos Basin

Zhang Yuhang1,2,3, Zhao Jingzhou3, Wang Yongwei4, Liu Tao4, Wang Wenqiang3, Tang Wen3   

  1. 1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum(Beijing), Beijing 102249, China;
    2. Shandong Provincial Key Laboratory of Depositional Mineralization & Sedimentary Minerals, Shandong University of Science and Technology, Qingdao, Shandong 266590, China;
    3. School of Earth Sciences and Engineering, Xi'an Shiyou University, Xi'an, Shaanxi 710065, China;
    4. Research Institute of Yanchang Petroleum(Group) Co., Ltd., Xi'an, Shaanxi 710075, China
  • Received:2017-06-05 Revised:2017-11-19 Online:2018-02-28 Published:2018-03-12

Abstract: Based on the latest seismic data, geological understanding and exploration results in the Southwestern Ordos Basin, paleo-deformation characteristics of the 1st member of the Upper Paleozoic were studied using tectonic evolution analysis and paleo-structure restoration, and controlling effects of paleo-structure on hydrocarbon distribution were analyzed.According to the strata correlation, the sedimentary, deformation, and subsidence characteristics of the 1st member of the Permian Shanxi Formation are identified.The tectonic evolution and hydrocarbon accumulation stages revealed that the key periods of the Upper Paleozoic tectono-hydrocarbon accumulation are the Late Jurassic and the end of the Early Cretaceous in the Southweste.Through the restoration of Shan 1 paleo-structure in different tectonic evolution stages, the ancient structure of the Upper Paleozoic Shan 1 in Late Triassic, Late Jurassic and end of Early Cretaceous share similarities but also demonstrate gradual evolution through time.The paleo-uplift and paleo-slope are widely developed in the late Jurassic, while the western slope gradually narrowed and the Tianhuan Depression is formed at the end of the Early Cretaceous.Based on the analysis of tectonic deformation and hydrocarbon accumulation stages, it is believed that the Late Jurassic Shan 1 paleo-structure is the key factor controlling the distribution of the Upper Paleozoic gas reservoirs in the Southwest Ordos basin.Due to the lack of long-distance migration of the gas in the Upper Paleozoic reservoirs in the study area, the Early Cretaceous hydrocarbon charge is focused around the Late Jurassic ancient structure highs of Shan 1 member.Thus the hydrocarbon accumulation model is characterized by near-source or intra-source accumulation.

Key words: reservoir distribution, tectonic evolution, paleo-structure, Upper Paleozoic, Ordos Basin

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