Phase Equilibrium Conditions of Gas Hydrates for Natural Gas Solid Transportation and Storage

Natural gas hydrates are ice-like solid substances, which are composed of water and natural gas, mainly methane. They have three kinds of crystal structures of five polyhedra formed by hydrogen-bonded water molecules, and are stable at high pressures and low temperatures. They contain large amounts of organic carbon and widely occur in deep oceans and permafrost regions. Therefore, they are expected as a potential energy resource in the future. Especially, 1m3 natural gas hydrate contains up to 172Nm³ of methane gas, depending on the pressure and temperature of production. Such large volumes make natural gas hydrates can be used to store and transport natural gas. In this study, three-phase equilibrium conditions for forming natural gas hydrate were numerically obtained in pure water. The results show that the predictions match the previous experimental values very well. And, help gases such that ethane, propane, i-butane, and n-butane reduce the hydrate formation pressure at the same temperature.