Numerical Calculation of Equivalent Continuum Model for Fractured Reservoir Based on Meshless Generalized Finite Difference Method

Low permeability fractured reservoir has the characteristics of non-even and non-continuous fracture distribution. In this paper, the equivalent permeability tensor is used to characterize fractured reservoirs based on the equivalent continuum media model. The initial fracture network model is generated based on the geological fracture description data, and then the equivalent permeability tensor is determined by the equal flow fundamental. Therefore, the fractured reservoir can be approximated as an anisotropic reservoir by the continuous equivalent media model. The meshless generalized finite difference method is a natural multi-point flow calculation scheme. It uses Taylor’s formula and weighted least squares method to obtain a generalized difference approximation scheme for the spatial derivative of an unknown function in the node influence domain. Compared with the multi-point flow approximation, this method can deal with the anisotropic permeability tensor more conveniently and reduce the calculation cost to some extent. In addition, the computational domain discretization scheme based on the meshless point cloud is more suitable for the irregular geometry of the actual reservoir. This method avoids the difficulty of grid-like numerical computation, which is to generate high quality matched mesh characterizing boundary to ensure the stability of computation at the boundary. The effectiveness and computational performance of the proposed method are verified by the examples of complex boundary crack networks, and the sensitivity of the influence radius to the computational accuracy is discussed. In summary, this work provides a new idea for numerical simulation of low permeability fractured reservoir.