A fully coupled method to model fracture permeability change in naturally fractured reservoirs

We present a new approach to model the fracture permeability change in naturally fractured reservoirs by combining a finite difference method (FDM) for fluid diffusivity equation in a fracture network, a fully coupled displacement discontinuity method (DDM) for the global relation of fracture deformation and the Barton–Bandis joint deformation model for the local relation of fracture deformation. The method is applied to naturally fractured reservoirs under isotropic in-situ stress conditions and anisotropic in-situ stress conditions, respectively. The application of the new approach shows that the fracture permeability decreases with the pressure depletion under isotropic in-situ stress condition. Under highly anisotropic stress, it is possible that shear dilation can increase fracture permeability even as pore pressure decreases with production.