A Model To Predict Gas Hydrate Equilibrium and Gas Hydrate Saturation in PorousMedia Including Mixed CO2-CH4 Hydrates

摘要

Phase equilibrium of gas hydrates is altered in porous mediaas compared to bulk systems. Inside porous media, thethermodynamic potential of chemical components changes dueto molecular interactions with pore walls and due to the energyrequired to maintain capillary equilibrium. A pore-freezingmodel was developed that can be used to predict gas hydrateequilibrium for pure CH4, CO2 and mixed CH4-CO2 systems insaline pore waters for any given pore size distribution. Theimportant feature of this model is that it takes intoconsideration salting out phenomena, I.e. increase in saltconcentration due to gas hydrate and ice formation. It alsogives the gas hydrate saturation in porous medium. A newEOS developed for prediction of bulk gas hydrate equilibriumconditions, based on van der Waals - Platteeuw model, is usedin the pore freezing model and can also be used to calculateheats of formation of these hydrates for a given pore size andpressure. The results obtained from the model are comparedwith experimental results.