Seabed methane seeping is widespread around the world, affecting the ocean and the global carbon cycle. Natural gas hydrate (NGH) is an important physical way to have leaked CH4 sequestration. Hydrate formation kinetics is one of the key factors affecting methane capture efficiency. Varied dissolved CH4 concentrations due to different methane flux differences may affect the kinetic characteristics of hydrate formation, which is necessary to be unveiled. In this work, the effect of initial dissolved CH4 concentration on hydrate formation in static system was investigated by constructing different CH4 leakage flux conditions in simulated “Haima” cold spring environment. The experimental results showed that the increase of initial dissolved CH4 concentration accelerated hydrate formation, while the obvious promoting effect may depend on the higher dissolved CH4 concentration. Morphology experiments showed that under the condition of relatively high concentration of dissolved CH4, a large number of flocculent hydrates formed in the liquid phase, and induced the growth of CH4 hydrate toward the liquid phase. Combined with CH4 gas consumption analysis, it is believed that this phenomenon was related to the formation of porous CH4 hydrate. The results obtained in this study have important reference significance for understanding the mechanism of hydrate formation and evolution in the CH4 seeping environment.
Keywords CH4 hydrate formation, dissolved methane concentration, morphology, â€œHaimaâ€ cold seep