Development of a thermodynamic model for CH₄, CO₂, CH₄-CO₂ gas hydrate systems

Abstract

An equation of state (EOS) software module was developed for CH4, CO2, and CH4-CO2 gas hydrates using the van der Waals-Platteeuw model. The model is based on classical thermodynamics and is used to predict the thermodynamic behavior of gas hydrates including the pressure and temperature at which gas hydrates form. A numerical scheme was developed for solving I-H-V, Lw-H-V, and Lw-H-Lhc equilibrium conditions for bulk hydrate formation from pure water and hydrocarbon. The model was further extended to determine hydrate equilibrium conditions in the presence of porous media of different radii. The numerical scheme was modified to account for the effect of salt on hydrate phase equilibrium. The results obtained from the model were in close agreement with the experimental data reported in literature. The main contribution of this work is that the proposed model can predict hydrate dissociation pressures at temperatures above 285 K more accurately than any of the available models.