Modeling Water-Injection Induced Fractures in Reservoir Simulation

Abstract

Abstract We couple a fracture growth simulator to a standard reservoir simulator using a two-way communication approach. The new approach allows interaction of two stand-alone software packages in order to capture the impact of both, varying reservoir pressure- and stress fields as well as dynamically growing or shrinking fracture shapes. At a given time step during the simulation, the pressure field is calculated by the reservoir simulator. We determine the stress field on the reservoir grid. Both, the pressure- and the stress field are needed to evaluate a fracture propagation criterion that is based on a stress intensity formulation. The fracture shape is determined in balance with the fracture fluid pressure and the in-situ reservoir stress field using an iterative procedure. Currently, the coupled simulator handles fracture growth/shrinkage for horizontally, symmetric fractures with fixed height in a single layer reservoir model. The stress calculations require the reservoir grid blocks to be sufficiently rectangular in shape. We benchmark the new simulator for a number of different test simulations by comparison. The overall comparison with analytical solutions and/or analytical simulations shows a very good fit.