On the influence of matrix flow in the hydraulic permeability of rough-walled fractures

Fractured porous media models may account for the influence of matrix flow in fracture permeability estimates through the slip boundary condition effect, i.e. permeable walls allow fluid to flow along them without viscous resistance. However, matrix flow may also create fluid pathways that unlock further fracture flow capacity, thus increasing its overall apparent permeability. We investigate this effect through numerical experiments by simulating fluid flow in a single fracture-matrix system with varying matrix permeability and calculating the apparent fracture permeability. We observe a consistent increase in fracture permeability with matrix permeability, which is yet underestimated by analytical models that factor in slip boundary conditions. Our study highlights the critical role of the surrounding porous matrix in accurately determining fracture permeability to prevent underestimations of the flow capacity of fractured porous media.