1. n. [Formation Evaluation]

The relationship describing the capillary pressure required to obtain a given nonwetting phase saturation in a rock. Rocks have a distribution of pore throat sizes, so as more pressure is applied to the nonwetting phase, increasingly smaller pore openings are invaded. The capillary pressure curve is important for understanding saturation distribution in the reservoir and affects imbibition and multiphase fluid flow through the rock.

See: wettability