Earth Science Frontiers ›› 2023, Vol. 30 ›› Issue (6): 316-328.DOI: 10.13745/j.esf.sf.2023.2.36

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Spatial-temporal distribution of fluid activities and its significance for hydrocarbon accumulation in the strike-slip fault zones, Shuntuoguole low-uplift, Tarim Basin

LI Huili1,2(), GAO Jian1,2, CAO Zicheng1,3, ZHU Xiuxiang1,3, GUO Xiaowen4, ZENG Shuai5   

  1. 1. Key Laboratory of Geology and Resources in Deep Stratum, SINOPEC, Beijing 102206, China
    2. Petroleum Exploration and Production Research Institute, SINOPEC, Beijing 102206, China
    3. Exploration and Development Research Institute, Northwest Oilfield Branch, SINOPEC, ürümqi 830011, China
    4. School of Earth Resources, China University of Geosciences (Wuhan), Wuhan 430074, China
    5. College of Geosciences, China University of Petroleum (Beijing), Beijing 102249, China
  • Received:2023-02-04 Revised:2023-03-05 Online:2023-11-25 Published:2023-11-25

Abstract:

The strike-slip faults in the Shunbei oil and gas field, Tarim Basin are essential for the reservoir formation and hydrocarbon accumulation. This research selects carbonate core samples containing fractured calcite veins from 23 drilling wells in eight major strike-slip faults in Shuntuoguole area to investigate fault-fluid interaction in the oil and gas field. Based on the petrography (diagenetic mineral types and cathodoluminescence characteristics) and lithogeochemistry (rare earth elements, strontium isotopes, carbon and oxygen isotopes) of calcite veins and laser ablation in situ U-Pb dating of calcite, the fractured calcite veins are divided into three types based on their formation environment and stage. Calcite veins formed in the first stage (474-444 Ma) are widely distributed in many faults, and their lithogeochemical characteristics indicate the diagenetic fluids are derived from formation water of the Middle-Lower Ordovician. Calcite veins formed in the second stage (441-403 Ma) are mostly distributed in fault zones east of Shunbei No. 5 fault, and Cambrian formation water and deep thermal fluids of the burial period are the sources of the diagenetic fluids. Calcite veins formed in the third stage (374-326 Ma)—with diagenetic fluids likely originated from deep thermal fluids—are only observed in a few samples from Shunbei Nos. 4 and 5 strike-slip faults and Shunnan area. In situ U-Pb dating results suggest the three calcite phases coincide with faulting events in the Middle Caledonian, Late Caledonian-Early Hercynian, and Late Hercynian, respectively. Moreover, the occurrence and characteristics of hydrocarbon-bearing inclusions in calcite veins imply liquid hydrocarbon charging during the Late Caledonian-Early Hercynian and Late Hercynian and crude oil cracking in the study area. The method of direct dating of strike-slip faults by in-situ U-Pb dating of carbonate minerals has broad applications, and the combination of in situ calcite U-Pb dating and hydrocarbon inclusion analysis can directly establish the time of hydrocarbon charging and evolution of dynamic hydrocarbon accumulation in a multi-cycle superposition basin.

Key words: calcite vein, fault-fluid coupling, hydrocarbon accumulation, Shunbei oil and gas field, Tarim Basin

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