Oil & Gas Geology ›› 2022, Vol. 43 ›› Issue (1): 54-68.doi: 10.11743/ogg20220105

• Petroleum Geology • Previous Articles     Next Articles

Division and formation mechanism of fault-controlled fracture-vug system of the Middle-to-Lower Ordovician, Shunbei area, Tarim Basin

Cheng Huang(), Lu Yun, Zicheng Cao, Haitao Lyu, Haiying Li, Yongli Liu, Jun Han   

  1. Northwest Oilfield Branch Company,SINOPEC,Urumqi,Xinjiang 830011,China
  • Received:2020-12-31 Revised:2021-12-18 Online:2022-02-01 Published:2022-01-28

Abstract:

Heterogeneous fractured-vuggy reservoirs of diverse genetic mechanisms are widely developed in carbonate strata, and the pore generation and evolution of diverse types within is related to the geological evolution of rocks. Generally, the formation of heterogeneous fractured-vuggy reservoirs is associated with thermochemical action mode of various unsaturated fluids in the formation and the total volume of materials that can be carried away. However, the fault-controlled fractured-vuggy reservoirs in Shunbei area, Tarim Basin, are not subjected to dissolution modification of unsaturated fluid, and feature a space distribution mainly constrained by fault zone boundaries. Exploration experiences have suggested that those reservoir spaces can be of hydrocarbon reservoirs with commercial value. What we have to pay attention to lies in whether a reservoir system of fracture-vug type can be formed under large-scale volume adjustment of materials by fault activities. An integration of 3D seismic interpretation, analysis of abnormal drilling conditions, well logs, element logging, pressure buildup test, interference test, and production performance data, is applied to comprehensively characterize the fault-controlled reservoirs, with their fractured-vuggy units and reservoir system inverted. The strain mode of brittle strata, factors controlling fault sealing, and water-rock interaction mode are studied according to the rock physical characteristics, structural compatibilization mechanism, and fluid modification mechanism during the strike-slip fault activity. It is proposed that the material volume variation resulted from rock dislocation, damage, and mechanical-thermochemical action in the fault zone, is a factor determining the formation of fault-controlled fractured-vuggy reservoirs in Shunbei area, whose pore system formation and evolution is closely related to fault activities. As theoretical derivation, the fault-controlled reservoirs can be subdivided into two types given the property and action mode of fluids, that is, the reservoir of karst type and of hydrothermal dissolution type, if being ignorable effects in the process of formation and evolution of their fracture-vug system.

Key words: fault-controlled reservoir, strike-slip fault, fracture-vug system, carbonate rock, Middle-to-Lower Ordovician, Shunbei area, Tarim Basin

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