Muhammed Asks PERM:
When displacing oil by water in a water wet reservoir, why does the interfacial tension increase when the oil thread gets smaller?
Dr. Jonathan Bryan from PERM Answers:
Interfacial tension is the force that has to be overcome to change the interfacial area between two immiscible liquids. The amount of surface tension has to do with how immiscible the liquids are. As such, interfacial tension should be a constant for a given oil and water, independent of wettability. I think maybe what you mean is how come the capillary pressure gets larger when the oil thread gets smaller? And for that, I think what you are saying is that the area of the oil thread is larger? So for that reason, the energy required to move the oil droplet will be larger, but its interfacial tension won’t change.
Energy to move the thread = IFT * area
Dr. Jonathan Bryan