Study on the Movement Pattern of the Dissociation Front of Natural Gas Hydrate

With the increase of global energy demand and the gradual depletion of traditional energy resources, natural gas hydrate (NGH) have attracted much attention because of their large reserves. At present, the main methods of hydrate extraction include depressurization, thermal stimulation and chemical inhibitor injection, etc. However, all of them suffer from the problems of low gas production and short stabilization time, which leads to the fact that hydrate has not yet been commercially exploited. In the extraction process, there exists a transition front region between hydrate dissociation zone and hydrate undissociation zone, and the fast or slow movement rate of the dissociation front will affect the hydrate extraction effect, so it is of great significance to study the movement regularity of the dissociation front of natural gas hydrate. In this paper, one-dimensional and three-dimensional models are established by numerical simulation to analyze the movement regularity of the dissociation front in the dissociation process of natural gas hydrate. The study shows that: in the one-dimensional and three-dimensional models, the dissociation front has a similar moving regularity, the dissociation front A moves rapidly and then nearly linearly, the dissociation front B moves slowly at the beginning, and then the moving rate becomes larger rapidly at the later stage of dissociation; under the same parameters, the moving rate of the dissociation front in the one-dimensional model is much larger than that in the three-dimensional model; with the saturation of the hydrate decreasing, the permeability increasing, the bottom hole pressure decreasing, the thermal conductivity increasing, the moving rate of hydrate dissociation front becomes faster gradually. The results of the study can provide a reference for the effective prediction of hydrate dissociation location and the early realization of commercial exploitation.