Numerical assessment of CO₂ geological sequestration in sloping and layered heterogeneous formations: A case study from Taiwan

Carbon dioxide geological sequestration (CGS) has been recognized as one of the potential solutions for reducing anthropogenic CO₂ emissions. The Changhua Coastal Industrial Park (CCIP) in central Taiwan has been preliminarily evaluated as a potential site for CGS. The CCIP site possesses sloping and layered heterogeneous formations with stagnant groundwater flow. Previous geophysical investigations of seismic reflection survey have found no significant faults near this site. Prior to the actual application of CGS in the field, it is important to carry out numerical simulations to predict the short- and long-term evolution of injected CO₂ into deep geological formations. In this study, the TOUGHREACT/ECO2N simulator is employed in order to conduct comprehensive CGS assessments at the CCIP site. Field scale CGS simulations are utilized to capture the details of the physical features, such as the displacement of saline brine by the injection of CO₂, buoyancy/gravity convection, and salt precipitation due to pore water dry-out, in the vicinity of the CO₂ injection well. Simulation results show that (1) the migration of CO₂ plume did not penetrate the low permeability formation at 500 years, (2) formation tilting caused a slightly asymmetric CO₂ plume oriented toward the up-tilt direction, and (3) the amount of solubility and residual gas trapping accounted for 26.8% and 19.0%, respectively, of injected CO₂ by weight at 500 years.