Abstract

Most recent studies on hydro-mechanical simulation of underground CO2 storage in saline aquifers have been focused either on the early reservoir life and short term migration of CO2 plume, or on near field scenarios in the vicinity of injection well. The main reason is the crucial computational cost that current coupling schemes and simulators carry out. Particularly, realistic inclusion of geomechanics into fluid flow processes is a bottle neck in hydro-mechanical coupling of large heterogeneous models of stress sensitive reservoirs with complex fluid flow and geomechanical physics. This work introduces a new coupling scheme between fluid flow and rock deformation, for rapid hydro-mechanical simulation of large heterogeneous reservoirs with elastic geomechanical constitutive behaviors. The technique is mainly about using of streamline simulations for hydro-mechanical coupling purposes. To assess the efficiency of the technique in terms of speed and accuracy, a large reservoir-cap rock system with relatively large number of grid-blocks was made. The speed and robustness of streamline-based hydromechanical coupling was investigated versus finite volume based flow-geomechanical simulations for the same model with the same geometry and physics. The concept of effective stress was applied in characterizing the stress state. The governing geomechanical and fluid flow equations were implemented based on mass and momentum balance equation for linear elastic materials. Forward flow streamline simulation was performed with 3DSL, which is developed on the FORTRAN platform. This paper first investigated the feasibility of inclusion of geomechanics in streamline simulation, and in the next step compared the efficiency and accuracy of the developed scheme to one of the conventional finite-volume based fluid flow-geomechanical simulations. The FV-FEA tool was developed based on Box-method (subdomain collocated finite-volume finite-element technique) to couple fluid flow and geomechanics to be compared with the so called SL-based hydromechanical coupling. The simulation results and comparative studies between two appraoches, demonstrated that the introduced technique is robust and increases the model efficiency and decreases the computational costs significantly. The approach also demonstrated to be helpful in hydromechanical coupling of CO2 storage, particularly for large domains and during the injection period.

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