Wettability is the relative adherence of different fluid phases to the substrate. This property has first order impact on multi-phase flow, and is therefore an important property for subsurface processes, e.g., oil recovery. Difference in fluid-substrate surface tensions between a displaced and displacing fluid then leads to a change in the free energy of the system. It has been suggested that this energy change can be used to quantify the wettability of the system. Such calculations are hampered by the fact that energy is expended on internal redistribution of fluids, e.g., Haines jumps. In this talk we will investigate the efficiency of quasi-static displacement processes.
This efficiency will be linked to the pore structure, in particular linked to the constriction factor for transport processes governed by the Laplace equation. We will use the efficiency to calculate the wettability for an imaged displacement. The calculated wettability is compared to measured contact angles inside the porous medium.