Comparison between equilibrium and kinetic models for methane hydrate dissociation

Current literature agrees that the equilibrium and kinetic models for methane hydrate dissociation are almost indistinguishable. In this comparison, we used the equilibrium and kinetic models with two kinds of thermal boundary conditions to study the dissociation of methane hydrates in porous media. We found significant deviations between the two models. A systematic parametric study of the kinetic reaction constants clearly shows that the kinetic model results approach the equilibrium model when the intrinsic mole dissociation constant excessively exceeds the range found in the literature. Further, we showed deviations in the dissociation pattern between the equilibrium and kinetic models for both boundary conditions. The equilibrium model exhibits a moving front pattern for hydrate dissociation while the kinetic model shows a moving zone pattern under adiabatic boundary conditions. As for the constant temperature boundary condition, the hydrate dissociates by shrinking in all dimensions for the equilibrium model while, for the kinetic model, it dissociates with no specific pattern throughout the entire reservoir. The parametric studies show that higher activation energy results in a lower rate of hydrate dissociation.

► Kinetic and equilibrium models for hydrate dissociation are claimed to be similar. ► We found deviation between the kinetic and equilibrium models for methane hydrate. ► Equilibrium predicts moving front dissociation while kinetic predicts moving zone. ► Both models are comparable in limiting case where kinetic constant is extremely high.