The Stefan moving boundary models for the heat-dissociation hydrate with a density difference

Highlights: • Generalized models of hydrate with a density difference were derived. • Stefan moving boundary was deduced by Rankine-Hugoniot conditions. • Exact solutions of temperature and dissociation frontier x_f were solved. • Effect laws on λ, x_f and T_inj were discussed compared with constant density. There exists a phase change for hydrate dissociation process during which is accompanied by a density difference, that also known as Stefan moving boundary problem. The conduction equations of the heat-dissociation hydrates are derived creatively for a semi-infinite slab reservoir. Based on the Rankine-Hugoniot jump conditions, the moving boundary condition of the dissociation frontier is innovatively deduced from a multidiscipline perspective. Exact solutions are derived in detail for the temperature distribution and the dissociation frontier location. Compared with models of the constant density, laws of the temperature and the frontier location are obtained for a sample hydrate reservoir considering some effect factors, such as various densities, heated-water temperatures and injection times.