3.1.1 Effect of changes in M on knw and kw
We plotted values of k nw for four values ofM (5, 2, 1, and 0.5) over the full realistic range ofS nw (10% to 90%) while holding log Canearly constant at −0.25 ± 0.1 (Fig. 2a). The k nwvalue increases as M increases, especially for intermediateS nw values (30% to 70%). For M = 5,k nw exceeds 1 in some S nwconditions; that is, it exceeds the intrinsic permeability of the rock. This result agrees with previous studies and can be explained by the lubrication effect, also known as the viscous coupling effect (Goel et al., 2016; Li et al., 2005; Ramstad et al., 2010; Yiotis et al., 2007; Zhao et al., 2017).