Fluid flow through anisotropic and deformable double porosity media with ultra-low matrix permeability: A continuum framework
Journal of Petroleum Science and Engineering, 200:108349, 2021.
Summary
A coupled continuum model is developed for fractured porous materials whose matrix and microfractures have sharply different permeabilities. The formulation combines anisotropic solid deformation with fluid transport through two interacting pore systems. Flow through the fracture network follows a generalized Darcy relation, with effective permeability obtained by upscaling geological information. In the less permeable matrix, a nonlinear low-velocity law accounts for threshold effects that conventional Darcy flow can miss. Exchange between the two systems depends on pressure difference, geometry, and interface permeability. An energy-balance argument supplies a thermodynamically consistent effective stress for the anisotropic poroelastic response. Numerical applications examine how coupling, material anisotropy, poroelastic coefficients, and the limited permeability of the matrix affect displacement and pore-pressure evolution. The framework also connects the continuum parameters to their physical origins and accommodates existing isotropic models as special cases.