Pore-Scale Investigation of Methane Hydrate Dissociation Using the Lattice Boltzmann Method

Fundamental understanding of pore-scale methane hydrate dissociation in porous media is important to evaluate submarine slope stability and potential utilization of methane resources. In this paper, a general pore-scale framework based on the lattice Boltzmann (LB) method is established for reactive transport coupled with nonisothermal multiple physicochemical processes in porous media. The framework combines the gas hydrate dissociation kinetic model, the single-phase flow LB model, the mass transport LB model, and the conjugate heat transfer LB model. The pore-scale framework is validated by several benchmark problems and then employed to investigate the endothermic dissociation process of methane hydrate with pore-filling and grain-coating habits in porous media. The methane hydrate endothermic dissociation behavior coupled with nonlinear nonisothermal multiple physicochemical processes involving intrinsic dissociation dynamics, gas flow, mass transport, phase change heat transfer, and conjugate heat transfer is well captured by the framework. The phase change of methane hydrate dissociation and pore structure evolution for different pore habits of hydrate are well depicted, and some insights about the dissociation front advancement and temperature distributions are also obtained. In addition, the effects of temperature field, inlet temperature, and inlet pressure on methane hydrate dissociation are investigated. The pore-scale methane hydrate dissociation helps to advance our understanding of permeability-saturation variation relation for continuum models.