Reservoir Simulation Integrated with Geomechanics

Abstract

Abstract Petroleum reservoir simulation has reached a point where it is desirable, and often necessary, to couple fluid and heat flow with the geomechanics of thereservoir and the surrounding rocks. The first step in this direction was Geertsma's hypothesis concerning pore compressibility in an elastic porousmedium, and its local relationship to fluid pressures. The evolution of thiscoupling of the solid matrix response to the changes in fluid pressure isdiscussed for materials with more complex behaviour than linear elasticity, andfor when temperature changes add new loads to the structure. A general coupledreservoir geomechanics model for thermal reservoir modelling is presented. Theresults of an implementation of this model are presented for coupled anduncoupled analyses of the stress and fluid pressure responses to cyclic steaminjection in a tar sand, a material with elastoplastic behaviour. The materialand fluid response to coupling was moderately different to that withoutcoupling, with principal stress rotations occurring at later times. The model, however, was also providing the complete distribution of stresses throughoutthe simulated domain, and the changes in porosity appropriate to a sandundergoing shear failure. These changes were noticeably different from thevariations in porosity obtained when only considering linear elastic porecompressibility.