Effect of Variable Brine Salinities on CO₂ Trapping: Implications for CO₂ Storage in Saline Acquires

Injecting CO₂ into the saline aquifer is considered to be an effective strategy to mitigate CO₂ emissions. Saline aquifers are known to have a wide range of salinities and several evidences showed that different brine salinities give rise to different CO₂-brine-rock wetting behaviors as well as different CO₂ solubility potential. This will ultimately influence the CO₂ plume migration behavior and the overall performance of a CO₂ sequestration project. However, associated field-scale CO₂ capacity predictions in different saline aquifers received little attention. This study conducts field-scale numerical simulations to analyze the effect of aquifer salinity on the CO₂ storage potential. Different CO₂-brine flow behaviors undervariablebrine salinities were considered. The results showed that an increase in the plume migration distance was observed in a higher salinity aquifer.While an increase in the brine salinity would result in an increase in residual trapping but a decreased solubility trapping capacities.Also, higher salinity formation observed more mobile CO₂ and thus exhibit a worse sealing efficiency. We point out that residual trapping capacity evaluation should consider both residual CO₂ saturation and the CO₂ occupied volume, which both are strong functions of brine salinity.