Numerical simulation of hydro-mechanical coupling in fractured vuggy porous media using the equivalent continuum model and embedded discrete fracture model

Abstract

In this study, an efficient numerical model is proposed to simulate the hydro-mechanical coupling in the fractured vuggy porous media containing multi-scale fractures and vugs. Specifically, an improved Equivalent Continuum Model (ECM), which is obtained through the asymptotic homogenization method, is applied to model micro fractures and vugs, while macro fractures are modeled explicitly by using the Embedded Discrete Fracture Model (EDFM) and non-matching grids. As an important feature of the explicit representment, the effects of fillings and fluid pressure on preventing macro fractures from closing can be considered. After that, the new mixed space discretization (i.e., Mimetic Finite Difference (MFD) method for flow and stabilized eXtended Finite Element Method (XFEM) for geomechanics) and fully coupled methods are applied to solve the proposed model. The mixed space discretization can deal with complex heterogeneous properties (e.g., full tensor permeability), and yields the benefits of local mass conservation and numerical stability in space. Finally, we demonstrate the accuracy and application of the proposed model to capture the coupled hydro-mechanical impacts of multiscale fractures and vugs on fluid flow in fractured porous media.