Methane hydrate (MH) is considered as one of the most promising energy source. It is necessary to understand the characteristics of methane hydrate formation and dissociation in marine sediments. In this study, the marine sediments from the South China Sea were employed to remold sediment core samples containing methane hydrates. Then, the MH-bearing sediment was dissociated by depressurization. The experimental results indicated that with the continuous supply of gas source, it is easier to nucleate and grow for methane hydrate in marine sediments under confining pressure. However, hydrate formation may lead to graincoating or contact-cementing pore, thereby not contributing to the gas flow. Thus, as the continuous gas injection causes the hydrate saturation to increase, the time required for inlet pressure raised to equal outlet pressure becomes longer and longer. In the later stage of depressurization, under the influence of confining pressure and fluid flow driving, water production and gas production in marine sediments are extremely difficult.
Keywords methane hydrate, formation, dissociation, marine sediment, confining pressure