Experimental study on the cold-seep methane hydrate formation kinetics

Cold-seep methane hydrates are widespread in the natural environment. A comprehensive understanding of the cold-seep methane hydrate formation kinetics is crucial for the knowledge of formation mechanisms and the development and utilization of natural gas hydrate. This study monitored the kinetics of methane hydrate formation in cold-seep fluids using continuous time-series Raman spectroscopy. A novel spectroscopic method was proposed to accurately determine the nucleation time of gas hydrates with a ten-second accuracy. Experimental results showed a smooth transition from dissolved methane to hydrated methane. Rapid hydrate nucleation and growth initiation were observed at the gas-liquid interface, forming hydrate films wrapping gas bubbles and suspending hydrate microcrystals in cold-seep fluids. Furthermore, a model for cold-seep methane hydrate formation kinetics was proposed, which indicated three distinct stages including an induction period, a metastable nucleation period, and a stable growth period.