3. Equilibrium Configurations of Fluid in PH and HH Pore Systems

Fig. 4 presents the equilibrium configurations of water and hydrocarbon and number density profiles (along z-direction) in 5 nm HH (Fig.4a-b) and PH (Fig. 4c-d) nanopores. We do not show the illite structure for clarity.
Fig. 4a shows a water film adjacent to the clay surfaces in the HH pore system. Water preferentially adsorbs on the surfaces because of the significant electrostatic force and hydrogen bond between water molecules and the surfaces75. This observation is analogous to water adsorption in silica-based pore structures69,76. Increasing the water concentration to 58.82% as shown in Fig.4b leads to an increase in the adsorbed film thickness. The number density of water (shown in the blue line) and hydrocarbon (black solid line) are relatively constant across the pore.