In petroleum engineering, the Leverett J-function is a dimensionless function of water saturation describing the capillary pressure,
where is the water saturation measured as a fraction, is the capillary pressure (in pascal), is the permeability (measured in m²), is the porosity (0-1), is the surface tension (in N/m) and is the contact angle. 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 is a characteristic length of the capillaries' radii.
This function is also widely used in modeling two-phase flow of proton-exchange membrane fuel cells. 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.
J-function in analyzing capillary pressure data is analogous with TEM-function in analyzing relative permeability data.
See also
Amott test
TEM-function
References
External links
http://www.ux.uis.no/~s-skj/ResTek1-v03/Notater/Tamu.Lecture.Notes/Capillary.Pressure/Lecture_16.ppt http://perminc.com/resources/fundamentals-of-fluid-flow-in-porous-media/chapter-2-the-porous-medium/multi-phase-saturated-rock-properties/averaging-capillary-pressure-data-leverett-j-function/ Leverett J-Function in Multiphase Saturated Rocks