Micro-Scale Investigation on the Permeability Evolution of Rough Fracture under Shear and Confining Pressure

Understanding the hydro-mechanical behavior of microfractures is critical for predicting permeability evolution in low-permeability formations. However, the coupled effects of shear displacement and confining pressure on fluid flow in rough microfractures remain insufficiently quantified. In this study, a realistic rough microfracture surface was reconstructed using micro-CT imaging and image-processing techniques. A series of numerical simulations were then performed using the finite element method to investigate fluid flow in fractures subjected to shear deformation and confining pressure. Results show that the distribution of aperture plays a dominant role in controlling fluid flow behavior within sheared microfractures: continuous bands of enlarged apertures form preferential flow paths and lead to pronounced channelization. Confining pressure induces progressive mechanical closure and an exponential decrease in permeability. To overcome the systematic overestimation of permeability by the classical cubic law, correction factors accounting for aperture heterogeneity and confining-induced closure were introduced. The corrected cubic law significantly improves permeability predictions for rough microfractures.