A quantitative study of salinity effect on water diffusion in n-alkane phases: From pore-scale experiments to molecular dynamic simulation

Direct Evidence of Salinity Difference Effect on Water Transport in Oil: Pore–Scale Mechanisms

“…Due to the chemical potential, water molecules diffuse from the LSW–oil interface toward the HSW–oil side. This hypothesis has been supported by molecular dynamic simulations to describe the trajectory of water molecules movements inside heptane phases . In the second scenario (Figure b), the surfactant molecules gather on the water–oil interface to minimize the free energy.…”

“…In order to prevent water films along the solid inner surface, we use a silanization solution of 1,7-Dichloro-1,1,3,3,5,5,7,7-octamethyltetrasiloxane to coat a hydrophobic surface inside the microchip. The details of silanization method can be found in our previous article . The contact angles of water, dodecane, and dodecane + SPAN80 droplets in air are ≈97°, ≈17°, and ≈10°, respectively, as shown in Figure .…”

“…The details of silanization method can be found in our previous article. 40 The contact angles of water, 29 All oil liquids are equilibrated with high-salinity water for 24 h. To investigate the emulsification effect, we added hydrocarbon-soluble surfactant SPAN 80 to both dodecane and heptane for creating the water-in-oil microemulsions in the oil phase. Span80 is a nonionic and hydrocarbon-soluble surfactant, which helps to form water-in-oil emulsions in the hydrocarbon liquids.…”

“…This hypothesis has been supported by molecular dynamic simulations to describe the trajectory of water molecules movements inside heptane phases. 40 In the second scenario (Figure 16b), the surfactant molecules gather on the water−oil interface to minimize the free energy. The concentration of surfactant molecules at water−oil interfaces depends on the salinity concentrations.…”

“…Therefore, they concluded that the oil inside an oil-wet porous medium acts as a semipermeable membrane, which induces the relocation of residual oil and has the capability of yielding additional oil recovery. Yan et al , have shown the osmotic effect on the oil remobilization from molecular to pore scale, based on various investigation tools including dynamic molecular simulation, microcapillary, and micromodel experiments. The results in the literature indicated that osmosis could increase oil migration and have a positive effect on oil recovery during low salinity water flooding.…”