AN ACCURATE FORMULATION O F THE SOLUBILITY O F CO, IN WATER, FOR GEOTHERMAL APPLICATIONS

The solubility correlations for the H,O-CO, system applied so far for numerical simulation of geothermal reservoir and well flows are crude. This is due, a t least partly, to the significant disagreement existing between the solubility models and results published in the specialized literature. In this work we analyze the reasons underlying this disagreement. On this basis, we propose a thermodynamically correct, and numerically accurate model for the solubility of carbon dioxide in water. Its range of validity is up to 350 ‘C and 500 bar. Our main contributions are: (a) the adoption of an equation of state for the gas phase that reallistically acounts for the non-ideal behavior of both components and that of the mixture, within the P-T range considered; and (b) to accurately include the effects of temperature and pressure on the solubility of carbon dioxide in the liquid phase. The proposed model fits the available phase equilibrium data for the H,O-CO, system nicely. In particular, it does not present the severe conflict between the linearity of the model and the lack of linearity of the data, evident in earlier models. The tight fit obtained with our model indicates that the complexities of H20-CO, phase equlibrium are well represented by it