Study on the multiphase heat and mass transfer mechanism in the dissociation of methane hydrate in reconstructed real-shape porous sediments.

As the first effort in literature, this paper conducts pore scale modeling on the methane hydrate dissociation and transportation in the reconstructed three-dimensional models of the MH-bearing sediment. The porous MH sample is synthesized using excess-gas method and imaged by micro-CT, which is used as input for the reconstructed mesh models. The real-time distribution of MH & water & methane, velocity and temperature is investigated. The effects of the temperature, pressure and flow rate of the injected water on MH dissociation and transportation are simulated and discussed. The results indicate that: 1) The hydrate generated by the excess - gas method is mainly cementing and mineral-coating on the sands surface, and occupies the small pores firstly. 2) The heterogeneity of the porous MH sediments is one of the key factors which influences the dissociation and the transportation process of the MH. 3) A lack of heat supply will restrict the dissociating rate of the MH reaching the maximum under the given PT conditions. 4) The gathering of the gas will decrease the flowing capacity of both water and methane. This study provides a new method to predict the multiple physicochemical and thermodynamical properties of the porous MH bearing sediments. • Pore scale MH dissociation and transportation in the real-shape porous media is modeled. • Real-time phase-change, multiphase flow, heat & mass transfer in porous media are studied. • Absolute and dynamic permeability of water & methane in the MH samples are predicted. • New method to predict petrophysical-thermal properties of MH sediments is provided. [ABSTRACT FROM AUTHOR]