The Model and Experiments of Solubility of CO2 in Saline with Complex Ions

Geological storage of CO2 is recognized as an effective way in reducing the greenhouse effect, and saline aquifers hold the greatest potential for CO2 storage. CO2 solubility in saline groundwater is a key parameter for assessing storage capacity in saline aquifer and CO2 leakage risk. Establishing models to predict CO2 solubility accurately with coexisting mixed ions is still a difficult problem. Based on the equations of state, this paper proposes a semi-empirical model to calculate CO2 solubility according to experimental CO2 solubility data. The solubility of CO2 in aqueous MgCl2 and CaCl2 solution was measured. New experimental apparatus was established specifically for the CO2 solubility measuring at the T-P-m range according to the geological reservoirs. The predicted values are proposed at a comprehensive combination of T-P-m. The average absolute deviation of CO2 solubility between the model and experimental results is 2.37 %, and the maximum absolute deviation is less than 5.146 %. The proposed model therefore possesses high accuracy and better adaptability to saline groundwater with mixed ions.