To obtain further insights into fluid cluster size and connectivity, we
considered the distribution of nonwetting and wetting fluids in one
section of a 2D slice of the simulated specimen for M = 1 andM = 5 at log Ca = −0.25 ± 0.1 and 50% saturation after the
simulation had converged (Fig. 5). The nonwetting fluid (red) atM =5 forms small, unconnected clusters in the pore throats, while
at M =1, the nonwetting fluid forms a large, connected cluster in
the pore throat. Thus, the nonwetting fluid clusters are larger and more
connected at M = 1 than at M = 5. Due to the increase of
number of nonwetting fluid clusters, the wetting fluid (green) atM =5 has more contact area with the rock surface compared toM =1, thus the wetting fluid receives more drag force from the
rock and causes decrease in relative permeability.