Hydro-Mechanical Numerical Analysis of Fault Reactivation Considering Fault-Zone Architecture in Clastic Reservoirs

Abstract

Geological faults are key discontinuities in sedimentary basins and strongly influence the hydraulic and mechanical behavior of hydrocarbon reservoirs. Fault zones typically contain a low-permeability core and a more permeable damage zone, generating sharp contrasts in petrophysical and mechanical properties. Stress variations from production, injection, or geological storage may induce fault reactivation, dilatancy, and permeability enhancement, yet many numerical studies still treat faults as homogeneous features. This study develops a two-dimensional coupled hydro-mechanical framework that explicitly represents fault-core and damage-zone domains incorporating viscoelastoplastic behavior through a Mohr–Coulomb model with Perzyna viscoplasticity. The novelty of this approach lies in integrating realistic geological architecture with explicit core-damage-zone contrasts and coupled viscoelastoplastic analysis under production and injection scenarios in compartmentalized reservoirs. Based on seismic interpretation of the Laurentian Basin (offshore Canada), CODE_BRIGHT simulations model single-phase flow in a deformable reservoir to evaluate stress redistribution, permeability evolution, and deformation. Sensitivity analyses indicate that an injection pressure of 6.5 MPa triggers fault reactivation, causing dilation-induced permeability increases and establishing hydraulic communication between the deep reservoir and the overlying aquifer previously sealed by Faults 01 and 02. Fault reactivation induces an asymmetric deformational field, with horizontal displacements of approximately + 25 cm along Fault 02 and − 13 cm along Fault 01, and a distortional vertical response characterized by a dip-slip response with differential block-scale subsidence and uplift, with a maximum subsidence of ~ 7 cm. Shear stresses concentrate mainly along Faults 01 and 02, particularly near their tips, indicating stress redistribution toward Fault 03. These results underscore the importance of internal fault-zone heterogeneity in controlling deformation, stress evolution, and transmissivity, with implications for CO 2 storage, geothermal systems, industrial injection, and geotechnical applications.

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