Radial mathematical model for hot water dissociation frontal brim of natural gas hydrates

Based on the description of dissociation process of natural gas hydrate in a semi-infinite zone, a radial pseudo-stationary mathematical model of heat transfer was built with Stefan moving boundary, and accurate solution of temperature applied in dissociation zone and natural gas hydrate zone was calculated by using Paterson method of exponential integral function. In addition, the location of dissociation frontal brim of natural gas hydrate was determined by combining Deaton method with Clausius-Clapeyron equation for decomposition heat. Radial dissociation laws of natural gas hydrate were obtained through an example of a steady hydrate reservoir whose physical parameters are known: with the increasing of radial range, temperature of hydrate reservoir drops abruptly to 8.416°C (dissociation temperature) and further to 5.33°C (reservoir temperature), and the location of dissociation frontal brim changes slowly; besides, with the increase of time, the temperature rises sharply after increasing slowly from 5.33°C to 8.416°C, and after adequate days will reach 100°C (the injected hot water temperature); furthermore, radius of hydrate dissociation grows slowly, and after 150 days supposed dissociation temperature changes 27.3°C for 80~100°C and 49.3°C for 100~150°C.