Oil & Gas Geology ›› 2023, Vol. 44 ›› Issue (1): 125-137.doi: 10.11743/ogg20230110

• Petroleum Geology • Previous Articles    

Coupling relationship between formation of calcite veins and hydrocarbon charging in Middle-Lower Ordovician reservoirs in strike-slip fault zones within craton in Shunbei area, Tarim Basin

Jianzhang LIU1,2(), Zhongxian CAI1,2(), Changyu TENG1,2, Heng ZHANG1,2, Chen CHEN1,2   

  1. 1.Key Laboratory of Tectonics and Petroleum Resources,Ministry of Education,China University of Geosciences (Wuhan),Wuhan,Hubei 430074,China
    2.School of Resources,China University of Geosciences (Wuhan),Wuhan,Hubei 430074,China
  • Received:2022-06-06 Revised:2022-10-18 Online:2023-02-01 Published:2023-01-13
  • Contact: Zhongxian CAI E-mail:liujzh@126.com;zxcai@cug.edu.cn

Abstract:

Shunbei oil/gas field is of the ultra-deep carbonate type controlled by multi-stage strike-slip faulting within the craton. The significant differences on the oil/gas property and abundance are shown in different fault zones even different segments in a fault zone. An integration of the core and thin section observation, cathodoluminescence, in-situ trace and rare earth element (REE) analysis, systematic analysis of fluid inclusions, is applied to study the sequence of fracture vein formation, sources of vein-forming fluids and their coupling relationships with hydrocarbon charging in the Middle-Lower Ordovician reservoir of the No.1 and 5 strike-slip fault zones in Shunbei area. We also investigate the factors controlling differential hydrocarbon accumulation in Shunbei area while understanding the evolution of strike-slip faults and the hydrocarbon accumulation pattern. The results show that there are at least four phases of calcite vein development, that is, Cal-1, Cal-2, Cal-3, and Cal-4, respectively, in the Middle-Lower Ordovician reservoir of the No. 1 and 5 strike-slip fault zones in Shunbei area. The vein-forming fluids of Cal-1 are mainly sea-sourced fluids, while that of Cal-2, Cal-3 and Cal-4 are derived from diagenetic fluids in the reservoir where the veins occur. The formation of Cal-2, Cal-3 and Cal-4 calcite veins is associated with tectonic activities and hydrocarbon charging in the Late Caledonian to Early Hercynian, the Late Hercynian to Indosinian, and the Yanshan-Himalayan, respectively. The strike-slip fault zones are different in hydrocarbon charging, as shown by that the main charging phase of the No. 5 fault zone was during the Late Hercynian to Indosinian, while the main charging period of No. 1 fault zone was during the Late Hercynian to Indosinian, and Yanshan-Himalayan. The differential hydrocarbon charging controlled by strike-slip fault structural style and evolution history is the key to differential hydrocarbon accumulation in Shunbei area.

Key words: calcite vein, strike-slip fault zone, differential hydrocarbon accumulation, hydrocarbon charging, ultra-deep stratum, carbonate oil/gas field, Shunbei area, Tarim Basin

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