The competitive diffusion mechanism of helium and methane in quartz nanopore by molecular simulation
Helium molecules possess unique characteristics such as small size,strong diffusion,and permeation capabilities,which significantly constrain the accumulation of helium gas.Therefore,a thorough understanding of the competitive diffusion mechanisms of helium and methane under geological conditions is crucial for systematically understanding the mechanism of helium gas accumulation.This study,for the first time,employed molecular simulation techniques to construct a model of quartz nano slit and nanochannels,investigating the competitive diffusion behavior of helium and methane mixtures in this model.Simulation results show that CH4 inhibit the diffusion of helium and can replace the adsorbed helium.When the helium concentration in the mixed gas reaches 90％,free helium gas molecules can aggregate to form larger helium clusters.The emergence of helium clusters has important implications for helium storage and the construction of underground helium storage.Additionally,CH4 and He cannot diffuse out of the quartz nanochannels when the diameter of diffusion channel pores is less than twice the kinetic diameter of CH4 and He.This is due to the strongest repulsive forces between molecules,preventing further dispersion of gas molecules.This study provides insights into the competitive diffusion mechanisms of helium and methane within quartz nano pores at the atomic-molecular level,offering valuable information for understanding the mechanisms of enrichment and preservation mechanisms of helium,and serving as a reference for the exploration and development of helium resources.
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