Modeling the self-preservation effect in gas hydrate/ice systems

Molecular dynamics simulations were performed to investigate the possible role of ice shielding in the anomalous preservation of gas hydrates. Two cases of ice shielding were considered: immersion of hydrate particles into bulk ice Ih and wrapping of similar particles in a thin ice shell. For a microscopic-level model of methane hydrate clusters immersed in bulk ice the excess pressure in the hydrate phase at 250 K was found to be sufficient to shift the gas hydrate into the region of thermodynamic stability on the phase diagram. For the second model the temperature dependence of various properties of the hydrate/ice nanocluster was studied. The surface tension estimates based on the Laplace equation show non-monotonic dependence on temperature, which might indicate the possible involvement of hydrate/ice interfacial phenomena in the self-preservation of gas hydrates.