A simple model for the prediction of mutual solubility in CO2-brine system at geological conditions

Abstract Reliable and accurate prediction of phase-partitioning behaviors in CO2-Brine system over a wide range of temperature, pressure and ionic composition (T–P–msalts) is of fundamental and practical importance to many geological-, energy-, and environmental-related technical applications. In this work, a simple model for the prediction of mutual solubility in the systems of CO2 + H2O and CO2 + Brine containing Na+, K+, Ca2+, Mg2+, Cl−, and SO42− is proposed, which can cover the typical geological conditions (0–250 °C, 0–200 MPa). Validation of the model calculations against updated experimental data available indicates that the simulation errors for CO2 solubility in pure water and brine are 6.899% and 8.08%, respectively, whereas the simulation error for water content in the CO2 rich phase is 9.67%. Compared to conventional complicated models, the proposed model is capable of simultaneously predicting CO2 solubility in aqueous phase and water content in CO2 rich phase, and obtains a comparable accuracy over a large T–P–msalts scale. The simulation results demonstrate that the developed model can reproduce the abrupt variations in phase compositions during the phase transition of the CO2 rich phase, and describe the influence of different ions on CO2 solubility. More importantly, the model is explicit, derivative-continuous and does not require iterative algorithms for its use, which means that it is computationally efficient and reliable to be incorporated into a large-scale multiphase flow simulator in geological processes.