Effect of Methane Solubility on Hydrate Formation and Dissociation: Review and Perspectives

Methane solubility in water is the foundation to make full sense of the mechanism of hydrate formation and dissociation. It is significant for realizing the safe and efficient exploitation of natural gas hydrate (NGH). This review discusses the calculation of methane solubility in gas-water and hydrate-water equilibrium systems, based on the hydrate phase equilibrium model theory, and the parameters used in the calculation process are described in detail. In addition, the influences of bubbles, capillary pressure, and salt on methane solubility are revealed. The difference in fugacity between the water phase and hydrate phase caused by the undersaturation of methane induces hydrate dissolution. Water injecting is a promising auxiliary method for hydrate exploitation, which will flush out the sand and gravel accumulated during the depressurization process. A novel hydrate exploitation method, which combines depressurization and a water injection method using double-split wells, is proposed. This novel method provides a new idea for efficient and sustainable exploitation of hydrate.