Fig. 10 Distribution of water at 0.002 nm/ps2and Cw = 71.43% in 5nm, 10nm, 15nm HH pores. The hydrocarbon molecules
are not shown. The result indicates that at each pore size, the peaks
and troughs in the velocity profiles correspond to the local density of
each of the phases.
We also note that the concentration of water and pore size can also
change the distribution of hydrocarbon and water. At specific water
concentrations (Cw = 71.43% and pore size= 10 nm), we can also observe
water bridges in HH nanopores.
4.2 Fluid Transport in PH
Nanopores
In the previous section, we reviewed transport of water and hydrocarbon
in HH pore systems where water bridges are largely absent except under
some specific conditions. In this section, we present the corresponding
results for PH pores where water bridges are prevalent across multiple
pore sizes and water concentrations.
The water and hydrocarbon velocity profiles for 54 NEMD simulations in
PH nanopore are provided in Figs. S6-7 in Supporting Information. In
this section, we only analyze a few representative hydrocarbon-water
velocity profiles in PH nanopores and address the effects of pore size,
water concentration and electric
field (the effects of acceleration
are provided in Supporting Information).
Effect of Pore size
Fig.11 shows the water (Fig.11a) and hydrocarbon (Fig.11b) velocity
profiles at an acceleration and water concentration of 0.002
nm/ps2 and 71.43% respectively in different PH
nanopore sizes. Water and hydrocarbon velocities increase with an
increase of pore size which is in agreement with Liu et
al.41. Additionally, water and hydrocarbon velocity
profiles are parabolic in the 5 nm PH nanopore and show flatter profiles
for the 10nm and 15nm pores with increasing distance from the pore walls
and the accompanying decrease in fluid-pore wall interactions.