An experimental study was performed to visually observe the driving force dependence of hydrate growth in a porous medium filled with either liquid water and dissolved CO2 or liquid water and gaseous CO2. The given system subcooling, ΔTsub, i.e. the deficiency of the system temperature from the triple CO2-hydrate-water equilibrium temperature under a given pressure, ranged from 1.7 K to 7.3 K. The fine dendrites initially formed at ΔTsub = 7.3 K changed quickly into particulate crystals. For ΔTsub = 1.7 K, faceted hydrate crystals grew and the subsequent morphological change was hardly identified for an eight-day observation period. These results indicate that the physical bonding between hydrate crystals and skeletal materials becomes stronger with decreasing driving force, suggesting that the fluid dynamic and mechanical properties of hydrate-bearing sediments vary depending on the hydrate crystal growth process.
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