In petroleum engineering, the Leverett J-function is a dimensionless function of water saturation describing the capillary pressure,[1] where
The function is important in that it is constant for a given saturation within a reservoir, thus relating reservoir properties for neighboring beds.
The Leverett J-function is an attempt at extrapolating capillary pressure data for a given rock to rocks that are similar but with differing permeability, porosity and wetting properties.
It assumes that the porous rock can be modelled as a bundle of non-connecting capillary tubes, where the factor
This function is also widely used in modeling two-phase flow of proton-exchange membrane fuel cells.
[2] A large degree of hydration is needed for good proton conductivity while large liquid water saturation in pores of catalyst layer or diffusion media will impede gas transport in the cathode.