Open Access

ARTICLE

Fracture Reactivation Modeling in a Depleted Reservoir

by Mengtao Cao^1,2, Weiguo Liang^1,2, Shunde Yin^3,*, Maurice B. Dusseault⁴

1 College of Mining Engineering, Taiyuan University of Technology, Taiyuan, 030024, China
2 Key Laboratory of In Situ Modified Mining of Ministry Education, Taiyuan University of Technology, Taiyuan, 030024, China
3 Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, N2L 3G1, Canada
4 Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, N2L 3G1, Canada

* Corresponding Author: Shunde Yin. Email:

Computer Modeling in Engineering & Sciences 2021, 126(1), 217-239. https://doi.org/10.32604/cmes.2021.011823

Received 01 June 2020; Accepted 21 September 2020; Issue published 22 December 2020

Abstract

Injection-induced fracture reactivation during hydraulic fracturing processes in shale gas development as well as coal bed methane (CBM) and other unconventional oil and gas recovery is widely investigated because of potential permeability enhancement impacts. Less attention is paid to induced fracture reactivation during oil and gas production and its impacts on reservoir permeability, despite its relatively common occurrence. During production, a reservoir tends to shrink as effective stresses increase, and the deviatoric effective stresses also increase. These changes in the principal effective stresses may cause Coulomb fracture slip in existing natural fractures, depending on their strength, orientation, and initial stress conditions. In this work, an extended finite element model with contact constraints is used to investigate different fracture slip scenarios induced by general reservoir pressure depletion. The numerical experiments assess the effect of Young’s modulus, the crack orientation, and the frictional coefficient of the crack surface on the distribution of stress and displacement after some reservoir depletion. Results show that the crack orientation significantly affects the state of stress and displacement, particularly in the vicinity of the crack. Slip can only occur in permitted directions, as determined by the magnitudes of the principal stresses and the frictional coefficient. Lastly, a larger frictional coefficient (i.e., a rougher natural fracture surface) makes the crack less prone to shear slip.

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Keywords

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