The OGS-Eclipse code for simulation of coupled multiphase flow and geomechanical processes in the subsurface

This paper presents a numerical simulation tool for the analysis of coupled processes related to subsurface operations. The tool combines the open-source scientific code OpenGeoSys with the reservoir simulator Eclipse enabling the coupling of thermal, hydraulic, mechanical and geochemical processes. While the coupling of multiphase flow with heat and reactive geochemical component transport has been already implemented, OpenGeoSys-Eclipse is now extended for the coupling of multiphase flow and deformation. By this, OpenGeoSys-Eclipse is capable of addressing the impact of pore pressure changes on rock stability and deformation as well as the feedback effects of geomechanical processes on multiphase flow via pore volume coupling and porosity and permeability update. The coupling is verified by several test cases of gas storage scenarios and compared with reference simulations of OpenGeoSys. The results are in good agreement regarding the general effects of geomechanical feedback on pore pressure as well as porosity and permeability changes. Differences in the results are only observed for the pore volume coupling arising from the different implementation of rock compressibility models in the two simulators. The simulations are furthermore used to investigate the relevance of addressing geomechanical feedback in numerical scenario simulations for the assessment of subsurface operations. The results show clearly, that, depending on the given storage site conditions and rock types, the feedback of deformation on pore pressure can be significant and should therefore be accounted for in the assessment.