Assessment of Geological Fault Reactivation Using a Fully Coupled Hydromechanical Embedded Finite Element Approach
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The pore pressure inside oil and gas reservoirs compartmentalized by sealing faults increases during injection processes. The rise in the pore pressure can induce fault reactivation by shear, tensile, or mixed modes, leading to geomechanical issues such as fluid leakage from the reservoir to other layers and seismicity [1]. Therefore, it is essential to accurately model the mechanisms involved in this problem, primarily related to the presence of a strong discontinuity, as a fault, inside the domain. Several numerical approaches can be used to represent the presence of discontinuities. The embedded finite element method (EFEM) has recently gained attention because it does not require the mesh to conform with the discontinuities [2, 3, 4], thus avoiding the mesh generation challenges of fault reactivation problems. Hence, this work proposes a fully coupled hydromechanical EFEM formulation based on the Strong Discontinuity Approach to investigate the potential risk of geological fault reactivation. An elastoplastic Mohr-Coulomb with a tension cut-off criterion governs the mechanical behavior of the discontinuity [5]. The hydraulic constitutive modeling of the discontinuity relies on the Cubic law to describe the longitudinal flow and on a leak-off parameter to control the transversal flow across the discontinuity. A discrete fracture model using zero-thickness interface elements is employed to validate the EFEM formulation. The numerical results demonstrate the EFEM capabilities to properly assess the fault reactivation mechanism and their injection pressure limits.
