Oil & Gas Geology ›› 2022, Vol. 43 ›› Issue (1): 69-78.doi: 10.11743/ogg20220106

• Petroleum Geology • Previous Articles     Next Articles

Internal architecture of strike-slip fault zone and its control over reservoirs in the Xiaoerbulake section， Tarim Basin

Qingyou Ma1,2,3(), Lianbo Zeng1,2(), Xuhui Xu4, Zicheng Cao3, Huashan Jiang3, Haixue Wang5   

  1. 1.State Key Laboratory of Petroleum Resources and Prospecting，China University of Petrolem （Beijing），Beijing 102249，China
    2.College of Geosciences，China University of Petrolem （Beijing），Beijing 102249，China
    3.Northwest Oilfield Company，SINOPEC，Urumqi，Xinjiang 830011，China
    4.Geophysical Research Institute，SINOPEC，Nanjing，Jiangsu 211100，China
    5.School of Geosciences，Northeast Petroleum University，Daqing，Heilongjiang 163318，China
  • Received:2020-12-24 Revised:2021-12-10 Online:2022-02-01 Published:2022-01-28
  • Contact: Lianbo Zeng E-mail:37337428@qq.com;lbzeng@cup.edu.cn

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Abstract:

The fault zone outcropping the Xiaoerbulake section in the northwest margin of Tarim Basin is selected to conduct detailed field investigation and description， sampling identification， geochemical analyses and other studies with the aim of establishing an architecture-reservoir model for a better geological description of fractured-vuggy reservoir bodies in the basin. The results show that the fault zone comprises right-lateral strike-slip faults （according to the juxtaposition relationship between the fault walls） and vertically cuts through the Middle Cambrian Shayilike and Awatage Formations. A dual structure of fault core and damage zone can be observed within the zone. The fault core is mainly composed of fault breccia with calcite veins. The angular and sub-angular shaped breccia is consistent with surrounding rocks in terms of lithology， indicating a possible damage-collapse-accumulation genesis of near-source material. The calcite particles in veins vary in size but tend to be finer toward the wall of breccia， indicating a multi-stage activities and reformation of fluids. With δ13C values ranging from -8‰ to -2‰， 87Sr/86Sr values generally higher than those of synsedimentary seawater， and significant negative Ce anomalies in REE （rare earth elements） analyses， the calcite veins truthfully record the visit of a later atmospheric fresh water. Fractures are well developed in the damage zone， most fractures are half or fully open with enlarged caverns from dissolution occurring locally along the fractures， and some fractures are filled by calcite cement. Based on the above research， a model is set up to describe the genetic evolution of the internal architecture and its control over the reservoirs in the fault zone. It suggests that the initial shear activity of strike-slip fault zone led to a brittle shear fracturing of the Middle Cambrian carbonate stratum， which then experienced long-term friction and slide to form noncohesive breccia and fracture zone with highly porous and permeable reservoirs. However， this strike-slip fault zone with high-quality reservoirs was later degraded into a vug-cemented fault zone as a result of multi-stage activities of calcite cementation jointly triggered by materials brought by atmospheric fresh water migrated vertically from surface to the deep along the zone and changes in temperature and pressure.

Key words: fault core, damage zone, internal architecture, reservoir-controlling pattern, strike-slip fault, Xiaoerbulake section, Tarim Basin

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