A discontinuous discrete fracture model for coupled flow and geomechanics based on FEM

A discontinuous discrete fracture model of coupled flow and geomechanics for fractured reservoirs is presented in this paper. Two problems of hydraulic fracturing and production are solved to prove the feasibility of the proposed model. The same grid nodes are shared by the flow and geomechanics parts, except the fracture junctions. Galerkin finite element method is used to discretize the flow equations and the mechanical equations. The meshing process is divided into two steps to avoid mesh concentration in the vicinity of the fracture. Implementing the discontinuous discrete fracture model is validated for three problems with analytical solutions and numerical solutions. Compared with the discrete fracture network model, the stress singularities in fracture tips can be captured by the discontinuous discrete fracture model. The discontinuous discrete fracture model can be used to simulate the fracture propagation. In this paper, the hydraulic fracturing process of four horizontal wells is simulated, and the production of each well is predicted with simulated hydraulic fractures. The methodology is then applied to simulate the production process of an artificially fractured shale oil reservoir containing intersected fractures. By slightly changing the mechanical condition on the fracture surfaces, we showed the importance of proppants in well production. The discontinuous discrete fracture model provides a more realistic description of the fracture aperture variation during the production process. More importantly, it offers a method to simulate the hydraulic fracturing and production processes in sequence. The design of infill-well fracturing can also be optimized with the proposed model.