Study on ethane hydrate formation/dissociation in a sub-millimeter sized capillary

Abstract

Study on the gas hydrates in porous medium has great significance to the formation, accumulation and exploitation of natural gas hydrate (NGH). Consequently, we investigated the formation/dissociation of ethane hydrate in a sub-millimeter sized capillary in this work, and observed the appearance and kinetic rate during the hydrate formation/dissociation process. The dissociation equilibria of ethane hydrate in capillary was measured first, then the influences of hydrate memory effect (dissociation temperature and time) and degree of subcooling on ethane hydrate formation were obtained, respectively. The results demonstrate that hydrate forms more difficultly in capillary than in conventional macro-reactor because of the fluid resistance effect and poor mass transfer of gas-liquid. The appearance and formation kinetics of ethane hydrate are greatly influenced by the memory effect and subcooling degree. The morphology of ethane hydrate formation on the bubble surface in water bulk phase shows that “bridge effect” occurs during the hydrate formation and growth in capillary.