Abstract: This work studies the thermodynamic model of hydrate equilibrium formation conditions in the porous media. Based on the van der Waals-Platteuw model of hydrate and Kelvin equation of capillary, a phase equilibrium computational model was built. Based on this model, the surface tension was further studied for methane and CO2 hydrate. Firstly, values of surface tension were regressed from experimental equilibrium formation conditions. It is shown that the surface tension increases with the temperature increasing and decreases with the pore radius increasing, moreover, it shows a near-line trend. Thus, the surface tension function of temperature and pore radius was proposed. Parameters of the function were optimized from experimental data with genetic algorithm. The result shows that the revised model with the correlated surface tension has a distinct improvement in the predicting the hydrate equilibrium formation conditions, average absolute deviations are 1.66% and 2.76% for methane and CO2 hydrates, respectively.

Key words: gas hydrate, porous media, surface tension, temperature, pore radius