| A model is developed for the calculation of phase equilibrium coupling with chemical equilibrium in the H2O-CO2-NaCl-CaCO3 system from 0 to 250°C, 1 to 1000 bar with NaCl concentrations up to saturation of halite. The vapor-liquid-solid (calcite, halite) equilibrium together with the chemical equilibrium of H+, Na+, Ca2+, CaHCO3+, Ca(OH)+, OH-, Cl-, HCO3-, CO32-, CO2(aq) and CaCO3(aq) in the liquid phase as a function of temperature, pressure, NaCl concentrations, CO2(aq) concentrations can be calculated with accuracy close to those of experiments in the stated T-P range, thus the first and second ionization constants of carbonic acid, calcite and halite solubilities, CO2 gas solubility, alkalinity and pH values can be accurately calculated. Using the specific ion-interaction equations of Pitzer to calculate activity coefficients, the model is also able to accurately predict the difference between dissociation constants and apparent dissociation constants, and the concentrations of all species at a given T-P-m condition. Using revised HKF equations to predict the dissociation constants of CaHCO3+ and CaCO3(aq), relative parameters are reevaluated and calculating equations are derived. Compared to previous models, this model covers larger T-P-m space and is much more closely reproduce experimental results, especially in the elevated pressure region. A computer code is developed and online calculation is also made available on www.geochem-model.org. Coupling with TOUGH2 code and program, an advanced numerical simulation model is developed to study CO2 geological storage in deep brine reservoir, which reserves the advantage of TOUGH2 on numerical simulation and improves its disadvantage on fluid-rock interaction. The primary simulation result shows it is practical that the multi-phase multi-component equilibrium model coupling with TOUGH2 program to simulate CO2 geological storage.
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