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Modélisation des propriétés PVTX des fluides du système H2O-gaz prenant en compte l'association par liaisons hydrogènes et les interactions dipolaires

Abstract : Modelling fluid-rock interactions as well as mixing and unmixing phenomena in geological processes requires robust equations of state (EOS) which must be applicable to systems containing water, gases over a broad range of temperatures and pressures. Cubic equations of state based on the Van der Waals theory (e. g. Soave-Redlich-Kwong or Peng-Robinson) allow simple modelling from the critical parameters of the studied fluid components. However, the accuracy of such equations becomes poor when water is a major component of the fluid since neither association trough hydrogen bonding nor dipolar interactions are accounted for.
The Helmholtz energy of a fluid may be written as the sum of different energetic contributions by factorization of partition function. The model developed in this thesis for the pure H2O and H2S considers three contributions. The first contribution represents the reference Van der Waals fliuid which is modelled by the SRK cubic EOS. The second contribution accounts for association through hydrogen bonding and is modelled by a term derived from Cubic Plus Association (CPA) theory. The third contribution corresponds to the dipolar interactions and is modelled by the Mean Spherical Approximation (MSA) theory.
The resulting CPAMSA equation has six adjustable parameters, which three represent physical terms whose values are close to their experimental counterpart. This equation results in a better reproduction of the thermodynamic properties of pure water than obtained using the classical CPA equation along the vapour-liquid equilibrium. In addition, extrapolation to higher temperatures and pressure is satisfactory. Similarly, taking into account dipolar interactions together with the SRK cubic equation of state for calculating molar volume of H2S as a function of pressure and temperature results in a significant improvement compared to the SRK equation alone.
Simple mixing rules between dipolar molecules are proposed to model the H2O-H2S binary system using a symmetrical approach. Calculated phase equilibria in the H2O-H2S, H2O-CO2, H2O-CH4 systems reproduced the experimental data within 7% of errors. Except for the H2O-CH4 system, binary interactions parameters estimated by fitting experimental data are closed to zero.
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Contributor : Erwan Perfetti <>
Submitted on : Thursday, February 14, 2008 - 2:45:39 PM
Last modification on : Wednesday, November 4, 2020 - 1:56:02 PM
Long-term archiving on: : Thursday, May 20, 2010 - 6:53:53 PM

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  • HAL Id : tel-00255940, version 1

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Erwan Perfetti. Modélisation des propriétés PVTX des fluides du système H2O-gaz prenant en compte l'association par liaisons hydrogènes et les interactions dipolaires. Géochimie. Université Henri Poincaré - Nancy I, 2006. Français. ⟨tel-00255940⟩

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