Lattice Boltzmann Simulation Of The Decomposition Characteristics Of Gas Hydrate In Porous Media

With the increasing consumption of fossil fuels in the world today,conventional energy sources are gradually depleted.Natural gas hydrate is hailed as an unconventional alternative energy source with great potential due to its wide distribution,abundant reserves,and high energy density.Natural gas is a mixture,mainly composed of alkanes,of which methane accounts for the vast majority.At the same time,the exploitation of natural gas hydrate is a process of coupling multi-physical fields such as gas-water flow,mass and heat transfer,and phase change in porous media.Its complicated and changeable process also brings great difficulties and challenges to mining work.Therefore,an in-depth understanding of the decomposition characteristics of methane hydrate in porous media provides a theoretical basis for the efficient exploitation and safe utilization of natural gas hydrate.This paper focuses on the above problems.First,based on the lattice Boltzmann method,a lattice Boltzmann model suitable for simulating the decomposition of gas hydrate under the gas-water-hydrate ternary system is constructed.In this model,the concentration difference is used as the driving force of decomposition,the fluid-solid interface tracing method is used to calculate the concentration change at the fluid-solid interface,and the gas-water two-phase flow process is simulated by the multi-component and multi-phase pseudo-potential model.Then,the constructed model was verified by the mass transfer model,the growth process of supersaturated solution hydrate,and the separation of gas and liquid components.Finally,the lattice Boltzmann model was used to simulate the decomposition process of methane hydrate in porous media,and the influence of factors such as porosity,inlet velocity,and occurrence state of hydrate on the decomposition characteristics of gas hydrate in porous media was discussed.The conclusions are as follows:(1)As the porosity decreases,the hydrate decomposition rate first increases and then decreases.Two main factors are interacting: the local pore rate and the accumulation of gas and water in the pores.(2)The greater the inlet velocity,the faster the decomposition rate of hydrate,and the greater the difference between the decomposition rate of the front and back sides of the hydrate.(3)In general,the decomposition rate of encapsulated hydrate is faster than that of pore-filled hydrate.