Compositional simulators are being increasingly used for modeling of green house gas storage in deep saline aquifers. It requires handling of chemical equilibrium reactions that occur between the injectant (normally CO2), reservoir water and the minerals. The composition of injected fluids, reservoir water, minerals and the operating conditions of pressure and temperature assume significance in such a scenario. This paper presents a framework for inclusion of chemical equilibrium reactions into an equation-of-state compositional simulator. Two main methods for modeling chemical equilibrium reactions, viz., element balance and primary species approaches are discussed and it is shown that both the approaches are equivalent. Methods for modeling gas solubility into the aqueous phase, and vaporization of H2O into gas phase are also presented along with examples showing the effect of aquifer mineralogy on the mineralization of CO2 and the dry-out and salt deposition due to water vaporization.

You can access this article if you purchase or spend a download.