Methane Hydrate Formation and Thermal Based Dissociation Behavior in Silica Glass Bead Porous Media

Abstract

Formation and thermal based dissociation of methane pore space hydrate has been studied at various initial hydrate saturations and heating rates utilizing a 1.3 cm 3 glass bead sample pack. Initial hydrate formation occurred rapidly after pressurization and proceeded at a higher rate for systems with the lower initial water saturation. Peak initial formation rates for 21%, 41%, and 60% initial water saturation was 4.3 × 10 −6 , 1.44 × 10 −6 , and 1.7 × 10 −6 mol/s, respectively. Three distinct stages of formation were observed for hydrate growth in porous media; a rapid initial formation regime determined by the enclathration reaction followed by a slow mass limited diffusion regime again followed by a second rapid and discrete formation period. Peak efficiency rates ranged from 74% to 81%. Experimental and numerical results showed slightly higher efficiency rates and maximum cumulative efficiency values for lower heating rate conditions. Lower heating rates produce a higher cumulative efficiency at the trade-off of less total hydrate being dissociated. Cumulative production efficiencies were greater for conditions of higher initial hydrate saturation, with values at 62% for 18% hydrate saturation and 72% for 50% hydrate saturation.

Evaluation of gas production from methane hydrates using depressurization, thermal stimulation and combined methods

“…During the experiment with the huff and puff in conjunction with the depressurization method, their results also show that the value of energy efficiency ranges from 15.6 to 41 at the steady process of gas production, which is lower than our results due to the high temperature of injection water (130°C). Therefore, the injection water with high temperature would yield higher rate of gas production; however, more energy would be consumed by the sensible heat of porous media, which would decrease the energy efficiency [21,28,38,39,67]. The results of the combined method show an obvious advantage in the energy efficiency, especially for the highly saturated hydrate-bearing sediments [21,28,38].…”

“…Therefore, the injection water with high temperature would yield higher rate of gas production; however, more energy would be consumed by the sensible heat of porous media, which would decrease the energy efficiency [21,28,38,39,67]. The results of the combined method show an obvious advantage in the energy efficiency, especially for the highly saturated hydrate-bearing sediments [21,28,38]. Compared with the warm-water injection method (Run 4-6), the energy efficiency for the combined method (Run 7-9) had increments of 13.32, 23.09 and 28.38, for S hi of 31.9%, 41.31% and 51.61%, respectively.…”

“…The thermal injection method could effectively improve the problems that emerged in the depressurization process, such as the low rate of gas production, the secondary hydrate formation or ice formation, the blocking effect, and the depletion of sensible heat [13,25,27,28]. In the field of thermal stimulation or heating studies, numerical simulations and experiments have been researched.…”

Energy from Waste Materials and Unconventional Sources

“…The most important characteristic of the sea water is the water temperature that its effects are very high on the physical and chemical changes in the sea water (Fitzgerald et al 2014).…”

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

“…The water content of the sediments was found to have a significant impact on the formation behaviors of gas hydrates. Fitzgerald et al [16] studied the formation behaviors of methane hydrate in the pore space of glass beads at various water saturations. They observed that the hydrate formation displays multistage formation behavior and the hydrate growth rate is higher for systems with the lower initial water saturation.…”