Geological storage of carbon dioxide by residual gas and solubility trapping

A CO2 geological storage technology based on residual gas and solubility trapping is proposed. First, we experimentally evaluated the maximum trapped CO2 saturation for typical conditions of aquifers at depths from 750 to 1000 m. To avoid the experimental difficulty due to the dissolution of CO2 in water and the compressibility of CO2, the trapped gas saturations were estimated from the relationship between pressure and volume under an isothermal expansion process. The trapped gas saturation is in the range from 24.8 to 28.2% despite the variation of CO2 density, viscosity and interfacial tension. Therefore, at least 38.8% of CO2 would be stored by residual gas and solubility trapping per unit volume as compared to physical trapping with cap rock. The storage potential of Japan by the proposed scheme is evaluated to be 71.6 Gt CO2, which corresponds to the emission in Japan for 53.6 years. The storage by residual gas and solubility trapping not only augments the storage capacity but also provides the sites that are located close to the large emission sources.