Progress in the research on the phase equilibrium of natural gas hydrates

Generally, the method of injecting some thermodynamic inhibitors as methanol or ethylene glycol, etc., into the production equipments and transferring pipelines to change the thermodynamic stable conditions so as to achieve the goal of restraining or avoiding hydrate formation in petroleum industry. Therefore it is quite necessary to predict the hydrate formation conditions under the case mentioned above. At present, the thermodynamic models of predicting the hydrate formation conditions are almost on the basis of classical statistical thermodynamics. The experimental determination of the phase equilibrium conditions of hydrates and the theoretical model of predicting the phase equilibrium conditions in an aqueous solution containing salts, alcohols and soluble polymers are comprehensively stated in detail and the major trend of studying the phase equilibrium of hydrates in the future is also proposed in this paper.