Impact of wettability heterogeneity on methane hydrate growth kinetics in partially water-saturated sediments

Gas hydrate formation in sediments is influenced by the availability of gas-water interfacial areas, which governs gas-water interactions. The surface wettability of sediment particles is expected to affect the spatial distribution of water within the pore space, thereby altering the extent of gas-liquid contact. Consequently, by tuning the wettability heterogeneity of the sediment, the spatial distribution of pore water can be regulated, which in turn influences the gas-water interactions and the kinetics of gas hydrate formation.

Sediments with spatial wettability heterogeneity were prepared by partially replacing hydrophilic silica powders with hydrophobic and moderately hydrophilic microparticles. The kinetics of gas hydrate formation in these partially water-saturated sediments were investigated and compared to reveal the influence of wettability heterogeneity on gas hydrate formation behaviors.

Compared with hydrophilic silica powders, the replacement with both the hydrophobic and moderately hydrophilic microparticles inhibited gas hydrate formation, with stronger inhibition observed for hydrophobic particles and at higher replacement fractions. Mechanistic analysis revealed that wettability heterogeneity altered the pore-scale water distribution, leading to thicker water films in hydrophilic regions and the formation of gas-filled pores in hydrophobic zones. The redistribution of the water reduced the gas-water interfacial areas and increased the mass transfer barrier, thereby suppressing gas hydrate formation. These findings highlight the pivotal role of pore-scale wettability heterogeneity in controlling gas hydrate formation kinetics, thereby offering valuable guidance for optimizing natural gas hydrate exploitation, understanding deep-sea methane transformation processes, and advancing hydrate-based technologies.