Effect of CO2 Injection Pressure on Oil Recovery and Reservoir Injectivity by Coupled Hydro-Mechanical simulation

In order to consider the geomechanical influence on the reservoir behavior, it is necessary to use a coupled model. We report here the development of an explicit coupled multiphase flow and geomechanical approach to analyze Hydro-Mechanical (HM) coupled processes relate to CO2 injection into oil reservoir by taking into account the limitations of production and injection. The explicit coupled study utilizes a reservoir model for simulation of fluid flow through porous media using the commercial reservoir simulator ECLIPSE and the optimized finite element discretization using the commercial finite element solver ABAQUS for the geomechanical analysis of rock deformation. The reservoir HM coupled models show that in the case of lower maximum bottom hole injection pressure, the cumulative oil production is more than other scenarios. Reservoir production and injection causes changes in the stresses and strains within the reservoir and surrounding rocks. Such changes give rise to the so-called geomechanical effects, namely the effects observed in the system due to the change in pore pressure, characteristic of the extraction and injection of fluids in porous media. In order to study the mechanical deformations during CO2 sequestration, numerical modeling of fluid flow through porous medium coupled with a geomechanical analysis of the medium at different pore pressure distributions is required. The fluid flow simulator (ECLIPSE) is executed first over a first period (built static and dynamic model). Updated pore pressures at the end of this first period are interpolated and transferred into the geomechanics grid in the geomechanical simulator (ABAQUS) using MATLAB code. Based on the updated producing conditions and constitutive relationships, the geomechanical simulator calculates the strains. Then the reservoir permeability and porosity are modified according to theoretical or empirical functions (between volumetric strain, permeability and porosity). Updated grid block permeabilities and porosities are then transferred to the fluid flow simulator for the execution of the next time period. The reservoir HM coupled show that in the case of lower bottom hole injection pressure, the cumulative oil production is more than other scenarios and at the high injection pressures, the production rates will not change with the injection bottom hole pressure variations. Also the FEM analysis showed that at CO2 injection pressure of 11000 Psi the plastic strain has been occurred in the some parts of the reservoir and the related stress path show a critical behavior.

Keywords:

geomechanics , explicit , coupled , permeability , porosity , FEM , plastic strain