A new approach to multiphase geochemical speciation modeling

Geochemical modeling based on equilibrium thermodynamics has become a recognized tool for understanding water–rock interaction processes and mechanisms. However, for the last 40 years, little attention has been given to the interaction of water–rock–gas systems or water–rock–gas–petroleum systems, possibly due to the complexity of the equilibrium calculations. The program described here is particularly useful for modeling geochemical interactions in oil and gas reservoirs, where brines and minerals are just some of the phases present, together with gases, and petroleum liquids, or other liquid phases. It all seems that, through a global minimization procedure, the equilibrium state of all the components (or pseudo-components) present in a hydrocarbon charged reservoir can be easily calculated at any pressure and temperature, by combining classical fluid phase equilibrium concepts, electrolyte theory, and solid–liquid equilibrium theory.