Densities for ternary system of CaCl₂-H₂O-CO₂ at elevated P-T: An experimental and modeling approach

Very few thermodynamic models exist for estimation of density alteration due to solution of CO₂ in a pure H₂O and CaCl₂-H₂O system. All of these models require density of CaCl₂ solution to estimate density of CaCl₂-H₂O-CO₂ system. Similarly, models presented to calculate CaCl₂ solution density need pure H₂O density in advance. The main approach to model density of CaCl₂-H₂O-CO₂ system is based on estimation of density alteration of CaCl₂-H₂O system due to the solution of CO₂ mole fraction. Hence, to estimate CO₂-CaCl₂-H₂O system density, density of CaCl₂ solution is necessary, and to estimate density of CaCl₂-H₂O system, density of pure H₂O is required in advance. Firstly in this paper, density of 0, 1.91, and 4.85 mol/kg CaCl₂ solutions saturated with CO₂ at 328.15 to 375.15^◦K and 68.9 to 206.8 Bar were measured through laboratory experiments. Then, a new model is developed to estimate the density of CaCl₂ solutions containing CO₂ based on the experiments conducted in this study. The average and maximum absolute deviations of the new model from the experimental data are 0.0047 and 0.0177, respectively. Hence, the new model combined with other existing models to separately calculate density of the CaCl₂ solution can be used to accurately predict density of the CaCl₂-H₂O-CO₂ system in a wide range of P-T applicable for subsurface reservoirs.