Hydrate Dissociation in Sediment

Summary An analytical model that describes hydrate dissociation under thermal stimulation in porous media is presented. The model views the dissociation as a process in which gas and water are produced at a moving dissociation boundary. The boundary separates the dissociated zone containing gas and water from the undissociated zone containing the hydrate. A similarity solution to the conservation equations is derived, and results are presented in graphical forms that are useful in numerical computations. In particular, heat fluxes, temperature profiles, and gas pressure distributions are presented for two cases that simulate saturated-steam and hot-water thermal stimulation. A parametric study showed that the dissociation rate is a strong function of the thermal properties of the system and the porosity of the porous medium. The energy efficiency of the dissociation process, defined as the ratio of the heating value of the gas produced relative to the heat input, was also computed. For hydrate thermal stimulation, an energy efficiency value of about nine was found, which appears encouraging for natural gas production from hydrate.