The penetration and displacement behavior of N2 molecules in porous interlayer structures containing a water/salt component with porosities of 4.29%, 4.73%, 5.17%, 7.22%, and 11.38% were explored using molecular dynamics simulations. The results demonstrated that the large porosity of the interlayer structures effectively enhanced the permeation and diffusion characteristics of N2. The water and salt in the interlayer structures were displaced during the injection of N2 in the porosity sequence of 4.29% < 4.73% < 5.17% < 7.22% < 11.38%. The high permeance of 7.12 × 10-6 indicated that the interlayer structures with a porosity of 11.38% have better movability. The strong interaction of approximately 15 kcal/mol between N2 and H2O had a positive effect on the diffusion of N2 and the displacement of H2O before it reached a stable equilibrium state. The distribution of N2 in porous interlayer structures and the relationship between the logarithm of permeability and breakthrough pressure were presented. This work highlighted the effects of porosity on the permeability and diffusion of N2/H2O in the interlayer, thus providing theoretical guidance for the development of petroleum resources.
Keywords: molecular dynamics simulation; penetration and displacement; porous interlayer structures.