RESERVOIR SIMULATION INTEGRATED WITH GEOMECHANICS

Petroleum reservoir simulation has reached a point where it is desirab le, and often necessary, to couple fluid and heat flow with the geomec hanics of the reservoir and the surrounding rocks. The first step in t his direction was Geertsma's hypothesis concerning pore compressibilit y in an elastic porous medium, and its local relationship to fluid pre ssures. The evolution of this coupling of the solid matrix response to the changes in fluid pressure is discussed for materials with more co mplex behaviour than linear elasticity, and for when temperature chang es add new loads to the structure. A general coupled reservoir geomech anics model for thermal reservoir modelling is presented. The results of an implementation of this model are presented for coupled and uncou pled analyses of the stress and fluid pressure responses to cyclic ste am injection in a tar sand, a material with elastoplastic behaviour. T he material and fluid response to coupling was moderately different to that without coupling, with principal stress rotations occurring at l ater times. The model, however, was also providing the complete distri bution of stresses throughout the simulated domain, and the changes in porosity appropriate to a sand undergoing shear failure. These change s were noticeably different from the variations in porosity obtained w hen only considering linear elastic pore compressibility.