Sensitivity of the CO2 storage capacity of underground geological structures to the presence of SO2 and other impurities

Depleted hydrocarbon reservoirs and deep saline aquifers are key targets for geological storage of CO2 to reduce atmospheric CO2 emissions. Most studies in CCS investigate subsurface storage of pure CO2. In this paper we investigate the impact of the presence of other gases (impurities) in the injected CO2 stream on solubility trapping (in the aqueous phase) and volumetric trapping (in the non-aqueous phase, for a wide range of pressure and temperature. Calculations for solubility trapping are based on an equation of state that accurately accounts for the pressure, temperature, gas-compositional (mixtures) and salinity influences on CO2 solubility and brine density. For volumetric trapping the Peng–Robinson equation of state is used, accounting for binary interaction for gas mixtures and density correction. In the analysis, special attention is paid to the impact of SO2, which exhibits anomalous storage effects when compared to other common impurities.