Mathematical models of the heat-water dissociation of natural gas hydrates considering a moving Stefan boundary

• Models of hydrate dissociation were exhibited considering Stefan moving boundary.
• Exact solutions of temperature distribution were obtained for hydrate dissociation.
• Location of dissociation front brim was deduced combing transcendental equations.
• Dissociation heat equations were obtained following the Clausius–Clapeyron equation.

This paper presents mathematical models for radial, quasi-steady state heat transfer in a semi-infinite hydrate reservoir with a moving boundary that is related to the dissociation of natural gas hydrates. The exact solutions of the temperature in the dissociation zone and hydrate zone, using the Paterson exponential integral function, are obtained, and the dissociation frontal brim location of the hydrates is determined by combining the Deaton method with the Clausius–Claperyron equation. A sample calculation shows that the reservoir temperature falls sharply to the dissociation temperature and then drops gradually with increasing distance to the reservoir temperature. With respect to time, the temperature increases slowly to the dissociation temperature, after which, the dissociation temperature falls sharply to the temperature close to that of the injected hot-water. By increasing the temperature of injected hot-water, more hydrates participate in dissociation; with an increase in time, the radius quickly increases, but the radius of hydrate dissociation increases slowly.