The model for solubility of CO₂ in saline groundwater with complex ions and the application on Erdos basin

To obtain accurate solubility of CO₂ is one of problems that need solutions urgently in CO₂ sequestration within saline groundwater. However, there are few data published for solubility of CO₂ under geological sequestration conditions. In order to fill the gap of the experimental study, the solubility of CO₂ in five formations of Erdos Basin was explored in this research. Groundwater samples in five reservoirs were carried out through an observation well in the Erdos Basin. The chemical composition was determined and experiments measuring CO₂ solubility were carried out in the synthetic water samples. Krichevsky-Kasarnovsky equation was established to analyze the experimental data. The relationship between concentration of K⁺, Na⁺, Ca²⁺ , Mg²⁺ and the solubility of CO₂ was analyzed and an excellent liner fit was found, which quantifies the impact of ions on the solubility of cO₂. Solubility data were compared to the model prediction over the temperature and pressure ranges of 318 ∼ 348 K and 8 ∼ 11 MPa. The average absolute deviation is 2.11%. The results can be used as a parameter for the evaluation of the CO₂ storage capacity in deep saline aquifer of Erdos Basin. (authors)