A Novel Meshing Routine for Modeling Reservoirs with Multiple Curved and Intersecting Faults in Coupled Flow-Geomechanical Dual 3D Grids

Abstract

We use a novel meshing routine to build a coupled flow-geomechanical model of injection and production in a caprock-reservoir-basement system with two conjugate curved faults that resemble a horst-graben or a synthetic-antithetic fault structure. The routine provides the 3D coordinates of each corner in the grid in a CMG grid file format. Our workflow enables us to represent the two faults as 3D objects to which we assign actual physical properties and dimensions of the faults. This is highly advantageous because traditional structured grids cannot represent curved faults, connected faults, or fault intersections without sacrificing either their geometry or their hydromechanical properties. Sacrificing the curved geometry of faults results in a loss of accuracy in computing the induced stresses in the basement region, which is known to host most of the recorded induced seismic events in US. The generated grid was used in a poro-elastoplastic simulation to examine stress changes resulting after production from a reservoir located in the hanging wall block (graben) region bounded by the two conjugate faults. The change in pore pressure due to production causes changes in both the total stress and the effective stress in the reservoir and the basement. The evolution of the shear and effective normal stresses on the faults may induce fault failure and slip depending on the fault rheology and friction parameters.