Iterative coupled analysis of geomechanics and fluid flow for rock compaction in reservoir simulation

Conventional reservoir simulators calculate the effect of rock compaction on pore volume change through the concept of rock compressibility under a defined loading condition (hydrostatic or uniaxial strain). This approach usually is appropriate for reservoirs with competent rock. For weaker formations and complicated rock compaction behavior, however, a coupled analysis of geomechanics and multiphase fluid flow may be required for obtaining more rigorous and accurate solutions from reservoir simulation. In general, computational efficiency and convergence of numerical solutions are two critical factors in order to make coupled analysis economically and numerically feasible for practical field applications. In this paper, an iterative procedure for coupled analysis of geomechanics and multi-phase flow in reservoir simulation is proposed for large-scale, full-field, 3D problems. The proposed procedure is general and effective for handling reservoir rock with complicated constitutive behavior of rock compaction and permeability change as well as for simulating various reservoir production scenarios. Descriptions of model formulations, constitutive equations, solution procedures, and strategies for enhancement of computational efficiency are presented in the paper. To demonstrate the capability of the developed procedure for iterative coupled analysis, several problems including a large-scale field example were studied and are presented.