Methane Hydrate Formation Kinetics in Varied Sediment of Deep-Sea Cold Seep Environment

The sediment types in deep-sea cold seep areas are highly diverse and compositionally complex. However, their influence on the kinetic characteristics of methane hydrate formation remains unclear. In this study, we examine the formation characteristics of methane hydrates for five primary minerals presented in the region of “Site F” cold seep. The results show that the specific surface area was a crucial factor influencing the hydrate formation kinetics at a low water saturation of 30 vol %. However, due to differences in the surface properties of the sediment media, the overall rate of hydrate formation exhibited a positive but no strictly proportional correlation with the specific surface area of the sediments. Although the specific surface area of chlorite was 12–19 times that of other sediment media, its water conversion rate in the first stage was almost the same to the other sediment systems, with about 8–12% per minute. When the water saturation increased to 60%, the hydrate formation rate decreased in all the sediments, and the effect of the specific surface area became ineffective due to the different water absorption capacities of the sediments. At 500 min into the experiment, the water conversion ratio for the chlorite and albite systems was approximately 40%, while about 55% for the potassium feldspar and quartz sand systems. The comprehensive analysis of four parameters related to hydrate formation kinetics revealed that chlorite possessed the strongest water-hydrate conversion ability for methane hydrates at a water saturation of 30 vol %. In the first stage of hydrate formation, the average water conversion rate reached about 11.6% per minute. However, at a water saturation of 60%, potassium feldspar and quartz sand had higher water-hydrate conversion ability. In the first stage of hydrate formation, it was about 2.45% per minute. These findings not only enhance our understanding of the fate of deep-sea methane seepage but also provide foundational data for developing submarine gas hydrates.