Investigation of CO2 Sorption Behavior i

Sorption isotherms, which describe CO₂ storage capacity of rocks, are important for estimating CO₂ sequestration potential of geological reservoirs. This study examined CO₂ sorption capacity of Kimachi sandstone and friable granite in the CO₂ rich dense phase, the condition of which is expected to occur mostly in the course of CO₂ injection geological reservoirs because of the displacement of formation water due to CO₂ pressurization in geological reservoirs acting to store CO₂ into aquifers, at geological temperatures and pressures. CO₂ sorption experiments were conducted using volumetric and gravimetric methods at temperatures of 35-320°C and pressures up to 20 MPa. It was found that Kimachi sandstone was capable of sorbing CO₂ into their internal structures. At 50°C, the amount of CO₂ sorption reached the maximum value of 1.4 mmol/g (1.34 scf/ton) for Kimachi sandstone and 0.7 mmol/g (1.57 scf/ton) for friable granite, respectively. Comparison among model predictions (monolayer adsorption, solubility, and pore-filling) suggests that the sorption of CO₂ onto rock minerals may contribute to a significant portion of the CO₂ storage capacity in the course of CO₂ injection. This investigation points out the significance of CO₂ sorption onto rock minerals for the possible CO₂ geological storage.