For conventional and enhanced geothermal reservoirs, faults and fractures are the main conduits for flow. In geomechanical simulations, empirical models are typically used to calculate the changes in fracture permeability due to stress application. However, determining the appropriate model parameters is often problematic due to the lack of available data and the difficulty of performing shear experiments. The displacement discontinuity boundary element method with integrated complementarity (DDM) is an advantageous alternative approach because it is a consistent physical model that simulates fracture permeability evolution under changing stress conditions. In this study, the DDM model was used to investigate the changes in permeability due to applied stress conditions for rough fractures. Fracture aperture maps for the different stress conditions were generated using the DDM model. Afterwards, a local cubic law model was used to calculate the fracture permeability. Results showed that the roughness of the fracture surface created stress interactions that led to local opening in the absence of a fluid within the fracture. The rough fracture surface also created heterogeneous fracture aperture and slip distributions. Overall, the fracture permeability and average slip increased with the shear stress magnitude and decreased with the normal stress magnitude. Moreover, it was demonstrated that the fracture permeability was higher in the direction perpendicular to the applied shear stress direction compared to the parallel direction.

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