Development of coupled two phase flow and geomechanics model to predict stress evolution in unconventional reservoirs with complex fracture geometry

Abstract

Understanding stress changes associated with reservoir depletion is very important for developments of unconventional reservoirs such as completion of infill well. Fluid flow in reservoir often contains multiple phases mostly a mix of oil and water phase. Multiphase flow in porous media also involves in many applications including water injection. In this paper, we have upgraded our coupled fluid flow and geomechanics with Embedding Discrete Fracture Model (EDFM) to two phase flow using OpenFOAM, an open-source platform for CFD, in order to expand the model to wider range of applications including characterization of stress evolution associated with depletion of two-phase flow in unconventional reservoirs with complex fracture geometries. Coupled geomechanics and fluid-flow was developed based on well-known fixed-stress split, which is unconditionally stable and computationally efficient to simulate how stress changes during reservoir depletion. EDFM was coupled to the model to gain capability of simulating complex fracture geometries using structured grids. The two phase model is based on Implicit Pressure Explicit Saturation (IMPES) method. Validations of our single phase model and EDFM were conducted in our previous paper. Validation of two phase model was done against analytical solution of Buckley-Leverett and Capillary-gravity equilibrium problems. In addition, validation of EDFM part was conducted against local grid refinement. The model was used to run performance test on water injection-oil production problem with geomechanics and capillary effect. Non-planar fractures under production was also used to test for EDFM part. Finally, we applied our model in simulation of 3D multiple fractures under production in a fully 3D reservoir. The results indicate that created fracture geometries have a significant effect on stress distribution and reorientation induced by depletion. Characterization of stress evolution due to reservoir depletion in two phase flow will provide critical guidelines for optimization of completion designs especially in infill well drilling and further development in unconventional reservoirs.