Any curved surface between two immiscible fluids has the tendency to contract into the smallest possible area per unit volume.
This is true whether the fluids are oil and water, water and gas (even air), or oil and gas.
When two immiscible fluids are in contact, a discontinuity in pres- sure exists between the two fluids, which depends upon the curvature of the interface separating the fluids.
We call this pressure difference the capillary pressure and it is referred to by pc.