Exploring the Self-Preservation Effect on Gas Hydrate Dissociation: A Comparative Analysis of Equilibrium and Kinetic Models in Permafrost Area

Selecting an appropriate reaction model for hydrate dissociation in porous media is essential for precisely predicting hydrate decomposition dynamics. The impact of ice on the dissociation of hydrates is a critical factor that affects the accuracy of NGHs resource development in permafrost regions. This research compares the equilibrium model and the kinetic model incorporating the self-preservation effect from ice to simulate NGHs dissociation during depressurization in permafrost. The results indicate that the kinetic model, which accounts for the self-preservation from ice, is crucial for accurate simulations when solid ice is present. In contrast, the equilibrium model, which ignores this effect, predicts slightly higher gas recovery rates. When no solid ice is present, both models yield similar predictions. Additionally, the self-preservation effect is most prominent in the early stages of production; later stages are primarily influenced by heat and mass transfer. Parametric studies indicate that a higher in initial hydrate saturation (SH) does not enhance gas recovery, instead increasing the discrepancy between the predictions of the two models. The changes in the area adjustment factor (FA) and reaction rate constant (k0) have little impact on the predictions of the kinetic model.