Numerical simulation of injection for CO ₂ geological sequestration with a treatment of CO ₂ dissolution into water

Carbon dioxide (CO ₂ ) is considered to be one of the greenhouse gases that may most contributes to global warning on the earth. Disposal CO ₂ from stationary sources into subsurface has been suggested as a possible means for reducing CO ₂ emissions into the atmosphere. However, much remains to be done in the issues regarding the safety and reliability of CO ₂ sequestration. In this study, we have developed a simulation code by using the mathematical model of multi-phase multi-component flow in porous media to analyze the flow dynamics in the subsurface. The equation of state for CO ₂ covering the fluid region from the triple point to supercritical region is employed to model the state of CO ₂ gas, liquid and supercritical state. The effect of CO ₂ dissolution in water on the injection behavior is taken into account by using Henry's law extended to CO ₂ /water system. The simulation was implemented under several geological conditions including gas, liquid and supercritical state to analyze optimal injection condition. The injection pressure is lowered at the lower temperature condition and the higher hydrostatic pressure condition. The lower injection pressure may prevent the fracturing of the injection well and excessive permeation of CO ₂ in the reservoir. The CO ₂ dissolution is slightly lowering the injection pressure and the effect on the injection pressure is negligible under the realistic hydrostatic pressure and temperature condition. It has been demonstrated that the simulation code developed in this study may be useful to provide fundamental knowledge required for the design of CO ₂ injection.