Study on the mechanism of self-preservation of gas hydrates

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To elucidate the mechanism of self-preservation of gas hydrates, the effects of electrolytes on the decomposition rates of methane hydrate (structure I), ethane hydrate (structure I), and krypton hydrate (structure II) were studied. Decomposition was significantly suppressed just below the eutectic temperature of the electrolyte + water system. When the concentration of the electrolyte was relatively high, however, a transitory upsurge in the decomposition rate occurred at the eutectic temperature. We speculate that the presence of electrolyte crystals increases the mobility of water molecules just below the eutectic temperature. This promotes the formation of a contiguous layer of ice that acts as an obstacle to diffusion of the evolved gas. However, when the temperature exceeds the eutectic temperature, the advent of stable liquid causes local melting of the ice layer with consequent weakening of the barrier for gas diffusion.