Xinjiang Petroleum Geology ›› 2022, Vol. 43 ›› Issue (5): 519-525.doi: 10.7657/XJPG20220503

• OIL AND GAS EXPLORATION • Previous Articles     Next Articles

Characteristics and Quantitative Prediction of Structural Fractures in Lei4 Member Reservoir in Pengzhou Area, Western Sichuan Basin

XIE Qiang1(), LI Gao1(), PENG Hongli2, HE Long2, GONG Hanbo1   

  1. 1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China
    2. Research Institute of Petroleum Engineering Technology, Southwest Oil and Gas Company, Sinopec, Deyang, Sichuan 618000, China
  • Received:2021-12-13 Revised:2022-04-12 Online:2022-10-01 Published:2022-09-22
  • Contact: LI Gao E-mail:xieqiang_swpu@foxmail.com;ligao@swpu.edu.cn

Abstract:

Structural fractures are found in the Lei4 member reservoir in Pengzhou area, western Sichuan basin. However, their distribution characteristics are unclear, which seriously affects the efficient development of natural gas in the Lei4 member. Through outcrop, core and rock thin section observations, the development characteristics of the structural fractures in the reservoir were described. The tectonic stress field during the Himalayan movement was simulated with the finite element method. Based on the rock failure criterion and elastic strain energy, the development of the structural fractures in the Lei4 member reservoir was predicted. The results show that the structural fractures in the Lei4 member reservoir are dominantly shear fractures with the extension ranging from 10 m to 70 m and the density of 5-10 fractures/m, mainly trending in NE-SW, NW-SE, nearly S-N and nearly E-W. Most of the fractures generated during the Himalayan movement are not filled. The minimum horizontal principal stress, maximum horizontal principal stress and differential stress of the Lei4 member during the Himalayan movement were 72.30-106.50 MPa, 126.00-183.47 MPa and 48.51-92.46 MPa, respectively. The predicted structural fracture density in the fault zone of the study area is far more than 15 fractures per meter, mainly 5-11 fractures/m in the Lei4 member. The fracture density in the high part of the anticline is lower than that in the two flanks, indicating that the distribution of fractures in the study area is controlled by both fault and structural position. The relative error between the predicted and measured structural fracture densities is 4.2%-10.7%, suggesting reliable predicted results, which provide a geological basis for the exploration and development of carbonate gas reservoirs in the Lei4 member in Pengzhou area.

Key words: Sichuan basin, Pengzhou area, Leikoupo formation, structural fracture, fracture characteristic, quantitative prediction, fracture density

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