Measurment And Modeling Of CO₂ Solubility In Formation Brine In Major Basins In North China

CO₂ has attracted much attention as the main factors leading to the greenhouse.Currently, carbon capture and storage（Carbon Capture & Storage, CCS） is recognized as an effective method to reduce CO₂ emission. The geological storage of CO₂ applies that the CO₂ has the characteristics of supercritical（when temperature is higher than304.2 K and the pressure is greater than 7.38 MPa）. It is injected into the deep underground to store, and the storage depth is usually more than 800 m. Depleted oil-gas reservoirs, unminable coal seams and deep saline aquifers are potential sites for CO₂ geological storage. Area of the widespread deep saline formations is large, and it can sequestrate CO₂ in geological time scale. It has great potential for CO₂ sequestration.The storage mechanism of CO₂ in deep saline layer mainly includes: gas storage,dissolution and mineralization. The amount of dissolution storage of CO₂ accounted for about 90% of the total amount of geological storage. Solubility is an important parameter to estimate the dissolution storage ability.Sedimentary basins in north of China are important sites for CO₂ deep saline aquifer storage, mainly including Qaidam Basin, Tarim Basin, Junggar Basin, and Bohai Bay Basin. Different saline have very different ionic compositions, thus their ability to dissolve CO₂ are different. Study about CO₂ solubility in different saline is necessary to calculate the aquifers’ storage ability. There are little studies for the complex-component solutions, especially for the certain saline aquifers.According to the specific geological and hydrological conditions of different basins,we selected some proper saline aquifers to study about. Eleven saline samples from Qaidam Basin, Tarim Basin, Junggar Basin, Bohai Bay Basin were selected. Solutions of synthetic saline were made up, and CO₂ solubility in the water at 313 K 353 K,pressure reach to 13 MPa was measured. Applying fugacity-fugacity method and using SRK equations of state, we proposed a semi-empirical model of the CO₂ solubility in pure water. The model can be used in CO₂ solubility in pure water at temperatures from313 K to 353 K and pressures from 5 MPa to 20 MPa with the average absolute error4.29%. According to the ratio of the CO₂ solubility in salt water and pure water, we formulated the model of CO₂ solubility in saltwater. The model which was established for CO₂ solubility in slain water have a maximum average error 4.45% in different concentration range. Thus, this model can simulate the CO₂ solubility in salt water of main basin in north of China well.