Methane Hydrate Formation in Marine Sediment from South China Sea with Different Water Saturations

The kinetics of methane hydrate formation in marine sediments with different water saturations are important to assess the feasibility of the hydrate production and understand the process of the secondary hydrate formation in the gas production from hydrate reservoir. In this paper, the behaviors of methane hydrate formation in marine sediments from the South China Sea at different water saturation levels were experimentally studied in isobaric conditions. The marine sediments used in the experiments have the mean pore diameter of 12.178 nm, total pore volume of 4.997 x 10(-2) mL/g and surface area of 16.412 m(2)/g. The volume fraction of water in the marine sediments ranges from 30% to 50%. The hydrate formation rate and the final water conversion increase with the decrease of the formation temperature at the water saturation of 40%. At the same experimental conditions, the hydrate formation rate decreases with the increase of the water saturation from 40% to 50% due to the reduction of the gas diffusion speed. At the water saturation of 30%, the hydrate formation rate is lower than that at the water saturation of 40% due to the effect of the equilibrium hydrate formation pressure, which increases with the decrease of the water saturation. The final water conversion is shown to increase with the increase of the water saturation, even the formation process at higher water did not end. The experiments at low water saturation show a better repeatability than that at high water saturation.