Coupling Fluid Flow and Rock Mechanics: Formulations of the Partial Coupling Between Reservoir and Geomechanical Simulators

M. Mainguy (1) , P. Longuemare (1)

1 IFPEN - IFP Energies nouvelles

During high porosity reservoir production, the rock compaction is a complex phenomenon that depends on the rock constitutive behavior, the reservoir stress path, etc. Reservoir compaction can hardly be analyzed with conventional reservoir simulators as the pore compressibility factor, the only mechanical parameter used in such simulators, is not sufficient to represent the complex phenomena involved. In order to solve correctly this problem, the full thermohydro- mechanical equations must be addressed. The corresponding set of equations can be either solved simultaneously (fully coupled scheme) or using a conventional reservoir simulator in conjunction with a geomechanical simulator and information exchanges between the two simulators (partial coupling). The paper presents three formulations of the partial coupling, which are obtained in the framework of single-phase flow and a linear elastic isotropic rock behavior. This simple framework makes possible an easy and rigorous derivation of the porosity correction to be appended to the reservoir Lagrange's porosity used in the reservoir simulator. The porosity correction depends on the pore compressibility factor and a mechanical contribution that can be expressed either in terms of volumetric strain, pore volume change, or the mean total stress change. One formulation is tested on a numerical test that depicts the water flood through a laboratory core sample initially saturated with oil and constrained to uniaxial strain. The numerical test illustrates the importance of the mechanical effects on the fluid flow problem and validates the partial coupling proposed. The example also highlights the role of the pore compressibility factor in the partially coupled reservoir simulation. Actually, in the partially (iteratively) coupled approach, the pore compressibility factor can be interpreted as a relaxation parameter controlling the convergence speed of the iterative process between reservoir simulation and geomechanical simulation.

Domaines: Physique [physics]

M. Mainguy, P. Longuemare. Coupling Fluid Flow and Rock Mechanics: Formulations of the Partial Coupling Between Reservoir and Geomechanical Simulators. Oil & Gas Science and Technology - Revue d'IFP Energies nouvelles, 2002, 57 (4), pp.355-367. ⟨10.2516/ogst:2002023⟩. ⟨hal-02043948⟩