Présentations Colloques

    Session 5.03: CO2 storage in deep saline aquifers and potential impacts on shallow aquifers
    Parmentier (orateur)
    Modeling the thermodynamic properties of CO2 aqueous solution following the HKF formalism
    Although the CO2-H2O geochemical system has been extensively studied, a thermodynamically-consistent model able to explain all experimental data (molar volume, heat capacity, reciprocal solubility) is still lacking. **The HKF (Helgeson, Kirkham, Flowers) equation of state [1] has been developed to model the standard thermodynamic properties of aqueous solutions taking account the ions and neutral solutes up to 5kbar and 1000°C. Following this formalism, Shock et al [2] proposed a set of HKF parameters for describing the thermodynamic behavior of dissolved inorganic gases like CO2. Since this original work, Shulte et al [3] modified some parameters to account for new experimental heat capacity data [4]. More recently, new measurements of the partial molar volume of aqueous CO2 have been published [5] which cannot be described with the existing set of HKF parameter. Therefore, there is a need to re-adjust them. **First, this work critically reviews the experimental data, including density and heat capacity of CO2 aqueous solution, and reciprocal solubility of CO2 in water. Then new HKF parameters are proposed to obtain agreement both with density and heat capacity of CO2 aqueous solution. To explain the reciprocal solubility data, two types of non-ideality are analyzed- the activity model in the aqueous phase and the fugacity correction in the CO2-rich phase. **The aim of this work is a unique model, thermodynamically consistent, able to calculate with an equal accuracy the reciprocal solubility, the density and the heat capacity of the CO2-H2O system in the T and P ranges relevant for CO2 storage. The same methodology should be applied with others gases (O2, N2, Ar, SO2 ...) to take into account the CO2 impurities.**References- [1] Tanger (1988) [2] Shock (1989) [3] Shulte (2001) [4] Hnedkovski (1997) [5] McBride-Wright (2015)


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