Abstract:

Hydrate dissociation front is one of objects of the field monitoring during gas hydrate production, and its velocity is closely related to the efficiency of gas hydrate production. However, there are few literatures about experimental data of the hydrate dissociation front. In view of this, an experiment of hydrate dissociation front induced by depressurization in unconsolidated sediment was developed. The hydrate saturation was measured by the time domain reflection measurement, and the movement of hydrate dissociation front was analyzed. An axisymmetric model for hydrate dissociation was proposed and its applicability was performed. A sensibility analysis for the velocity of hydrate dissociation front was carried out. Based on the experimental and numerical conditions, main conclusions were made as follows: first, propagation distance of hydrate dissociation front is approximatively linear with the square root of propagation time; second, velocity of the hydrate dissociation front decreases obviously when the propagation distance becomes longer; finally, velocity of the hydrate dissociation front increases when the reference value of the absolute permeability, initial gas saturation, and environmental temperature increase, however, it decreases when the initial hydrate saturation, reduction index, and outlet pressure increase.

Key words: hydrate-bearing sediment, depressurization, hydrate dissociation front, time domain reflection, sensibility analysis