Fracture pore network model: efficient pore scale modelling of fluid flow in fractured porous media

Fluid flow through fractured porous media occurs commonly in the subsurface such as the hydrocarbon flow in the fractured reservoirs. However, current discrete fracture modelling methods that simulate the transport processes in fractured porous media, using finite element method and lattice Boltzmann method, are computationally expensive. We have developed a new fracture pore network model (FPNM) to efficiently simulate the fluid flow properties in fractured porous media associated with the pore matrix.

We extend the idea of pore network models (PNM) (Blunt, 2017) to fracture pore network model by adding a new explicit fracture element in addition to the pore matrix that is traditionally idealised as pore body and pore throat elements. The fracture element is simplified as an ideal planar cuboid with properties of aperture, width, length and orientation. The complex pore structure can be represented by a topological network of pore bodies (nodes) and fractures, which are connected by pore throats (bonds). These three elements within the FPNM are assigned with the key features of pore structure.

The fluid flow between the fracture and the matrix in the FPNM with a single fracture is investigated first. The results are compared with finite element simulation by using COMSOL Multiphysics® (AB, 2018). The FPNM is then extended to include multiple non-intersecting fractures consequently. Pore networks with fracture elements were extracted from a couple of test images and the results are compared with finite element simulation in terms of permeability, flow rate and pressure. A reasonable agreement was achieved which demonstrates the value and efficiency of the fracture pore network models.