The Formation of CH4 Hydrate in the Slit Nanopore between the Smectite Basal Surfaces by Molecular Dynamics Simulation

Abstract

Natural gas hydrate (NGH) formation behavior in porous sediment influences the investigation of the reservoirs and the exploitation of NGH. However, its molecular mechanisms of NGH formation in the porous sediment remain unclear. In this work, we present the CH4 hydrate formation in the smectite system through molecular dynamics simulation. The microstructure molecular configurations and properties are analyzed. The results find the pure H2O solution and the CH4-H2O homogeneous solution in the initial configuration of the smectite layer reveal the different influence on the hydrate formation. The gas–water ratio (ri) affects the molecular diffusion and the hydrate formation. In the smectite layer, the two types of arrangements of cages are present: the semi-cage arrangement and the link-cage arrangement. The silicon-oxygen ring of the smectite surface connecting with the two types of arrangements of cages has the stable effect for the hydrate formation in the smectite.