Formation and occurrence characteristics of methane hydrate in the complex system of sodium dodecyl sulfate and porous media

In recent years, porous media have attracted a lot of attention due to the enhanced kinetics of hydrate formation. However, how porous media promote hydrate formation is still an open topic. In this study, two different porous media, activated alumina and glass beads (average particle size 1, 3, 5 mm), were mixed with sodium dodecyl sulfate (SDS) to promote methane hydrate formation (275.15 K, 6 MPa). The smaller the particle size is, the better the promoting effect of porous media is, corresponding to faster formation kinetics and higher gas consumption. The average hydrate formation rate (2.3 mmol/min) and T₉₀ (136 min) in the 1 mm activated alumina system was 2.6 and 0.4 times higher than the average hydrate formation rate (0.9 mmol/min) and T₉₀ (349 min) in the 3 mm activated alumina system, respectively. Better performance of activated alumina particles than that of glass beads because of its rich micropores and unique electric double layer distribution in solution. The gas storage density of hydrate in the 1 mm alumina system can reach 129.13 V_g/V_h, while the highest gas storage density of hydrate in the 1 mm glass bead system was 122.35 V_g/V_h, which was similar to that of hydrate in the 3 mm activated alumina system (123.63 V_g/V_h). The gas consumption of the system was not affected by mass transfer but was controlled by particle size and solution volume with the presence of SDS. Under supersaturated and saturated conditions, it is found that the porous media bed and hydrate layer moved upward under the action of capillary force and methane gas driving force. This work provides a reference for the formation and occurrence of hydrates with the presence of porous media and surfactants.