Stress-coupled simulation for fluid flow in fracture, matrix and across the interface in geothermal environment

This paper presents an innovative method to simulate fluid flow in fractured geothermal reservoirs. The geothermal reservoirs are considered at their full complexity, with variably oriented and intersected fractures with different sizes and irregular patterns. Fluid flows inside the matrix, fractures and fluid interactions between matrix and fractures are also taken into account. A boundary element method with periodic boundary conditions is used to calculate the permeability tensor in cells of jointed and fractured rock. A flux continuous model is used to implement the derived set of tensor in a finite volume simulation of the fluid flow, to estimate water production from the reservoirs. The finite element simulation is coupled and repeated for multiple time steps (unsteady state to quantify the effect of field stresses on the fluid flow and reservoir pressures. This integrated method is validated against results from analytical analyses. It is shown to balance the representation of physical complexity of the coupled processes with the need to avoid representing the complete set of discrete fractures in the problem domain, dramatically advancing the current state-of-the-art in the simulation of fluid flow through reservoirs with discrete fracture networks. Key-Words: Flow simulation, Discrete fracture network, Unsteady state, Field stress.