Simulation of CO2 injection in a small-scale pilot site in the Pohang Basin, Korea: Effect of dissolution rate of chlorite on mineral trapping

In Korea, a small-scale pilot project for CO2 injection was launched to target an offshore reservoir within the Pohang Basin. The objectives of this study are to present the effects of CO2 injection in a sloping aquifer on the evolution of the CO2 plume and its impact on mineral trapping using TOUGHREACT. The results show that the CO2 plume is asymmetrical and rapidly migrates along the slope in the up-dip direction from the injection well. With the migration of the CO2 plume, the increased acidity accelerates the water-rock interactions. As the CO2-water-rock interactions start quickly due to the rapid spreading of the CO2 plume, the amount of mineral trapping slightly increases due to the precipitation of siderite by chlorite dissolution. However, the stability of siderite is sensitive to the dissolution rate of chlorite. At low chlorite dissolution rates, siderite is more stable than ankerite in an undersaturated state. At high chlorite dissolution rates, ankerite is more stable because of the higher pH. In addition, the amount of mineral trapping increases considerably up to 3.7 kg/m3, which is about 90 times that at the initial rate (0.04 kg/m3). This simulation indicates that the uncertainty in the dissolution rate of chlorite must be considered when estimating the capacity of mineral trapping in situations in which iron-containing carbonate minerals significantly influence the mineral trapping.