Rock and Soil Mechanics ›› 2023, Vol. 44 ›› Issue (1): 159-170.doi: 10.16285/j.rsm.2022.6041

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Propagation process of hydraulic fracture crossing an orthogonal discontinuity

CHEN Lei 1, 2, ZHANG Guang-qing1, 2, ZHANG Min1, 2, CAO Yu-jie 3, SHEN Li-ji1, 2   

  1. 1. College of Petroleum Engineering, China University of Petroleum, Beijing 102249, China 2. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China 3. Oil and Gas Technology Research Institute PetroChina Changqing Oilfield, Xi’an, Shaanxi 710018, China
  • Online:2023-01-17 Published:2023-03-13
  • Contact: ZHANG Guang-qing, male, born in 1975, PhD, Professor, PhD supervisor, research interests: rock mechanics in petroleum engineering. E-mail:
  • About author: CHEN Lei, male, born in 1995, PhD candidate, focusing on rock elastoplastic fracture mechanics.
  • Supported by:
    the National Science Fund for Distinguished Young Scholars (51925405) and the Strategic Cooperation Technology Projects of China National Petroleum Corporation and China University of Petroleum-Beijing (ZLZX2020-02).

Abstract: Massive developed discontinuities are the salient geological features of unconventional oil and gas reservoirs, and the hydraulic fractures’ capabilities of crossing the discontinuities concern the stimulation effects of hydraulic fracturing. To study the development of the fracture process zone (FPZ) when the hydraulic fracture orthogonally propagates through a discontinuity, the self-designed visual fracturing equipment was adopted to carry out hydraulic fracturing tests on sandstone plates with a prefabricated unbounded friction interface. Based on the digital image correlation method, the displacement and strain characteristics during the hydraulic fracture propagation across the orthogonal interface were monitored in real time. The test results show that the FPZ has developed across the interface before the hydraulic fracture extends across the interface. Whether the fracture can propagate through the interface is predetermined at the initial developmental stage of the FPZ and is not affected by the stress-softening process in the FPZ. Based on the Renshaw-Pollard criterion, a criterion considering the FPZ boundary was established for estimating the fracture propagation across the friction interface, and it was verified by test data and existing results. In comparison, the improved criterion considers a more accurate application scope of elastic fracture mechanics at the fracture front. The aspect ratio of the FPZ has a significant effect on the improved criterion, and the lower limit of friction coefficient required for the fracture propagation orthogonally across the interface declines as the aspect ratio of the FPZ rises under the same conditions.

Key words: fracture mechanics, hydraulic fracturing, digital image correlation, geological discontinuities, fracture process zone