Numerical simulation of coupled fluid and geomechanics in fractured rock masses based on a discrete fracture-matrix model

Abstract

This paper presents a discrete fracture-matrix (DFM) model to simulate coupled fluid flow and geomechanics in fractured rock masses. Aiming at computational efficiency and accuracy, the fractures are explicitly represented by lower-dimensional zero thickness elements. The proposed numerical model is comprised of a matrix-fracture flow model, a matrix deformation model and a stress-strain constitutive model for the fracture deformations. Darcy's law is used to describe the fluid flow in both rock matrix and fractures. Variations of fracture aperture and permeability induced by fracture deformations are considered. A finite element code (COMSOL) is employed to numerically solve the coupled governing equations. To examine the efficiency and accuracy of the proposed model, three simulation cases are conducted in this work. The results obtained are validated against the corresponding analytical solution and published numerical results. The numerical model is then applied to study the coupled hydro-mechanical behavior of fractured reservoir bank slope. The simulation results show that the fractures in the slope result in greater fluid drainage and contribute significantly to deformations.