Flow simulation in 3D fractured porous medium using a generalized pipe-based cell-centered finite volume model with local grid refinement

The presence of fractures in porous media strongly influences the fluid flow behavior. This work presents an efficient and simple numerical model to address the hydrodynamic behavior of complex fractured porous media, aiming at balancing computational efficiency and accuracy. Fractures are mapped to a set of cells having implicit aperture, where local grid refinement (LGR) is adopted around the fracture to improve accuracy with lower computational burden. The fluid flow in the matrix, fracture, and exchange between fracture-matrix, are described by a generalized equivalent pipe-network model. The numerical scheme and implementation are verified against established numerical solutions. Results show that this method is efficient in capturing main phenomena of the fluid transport in fractured porous media, without sacrificing computational accuracy. Heterogeneous and anisotropic features of fluid flow are well captured. Particularly, the convergence of the LGR is in a higher order than the global grid refinement (GGR). This model also provides great flexibility in handling a multitude of fracture input data, e.g., planar fractures obtained from statistical data and non-planar fractures from digital images represented with point clouds. Balancing computational accuracy and efficiency, this method provides an effective approach for simulating flow transport in fracture porous medium.