The explicit form of physical correlations is given by following analytical formula:

P_{cow} (s_w) = \frac{ (\sigma \cos \theta) _{ow} } { \sqrt \frac{k}{\phi}} \; J_{cow}(s_w)

P_{cog} (s_g) = \frac{  (\sigma \cos \theta)_{og} } { \sqrt \frac{k}{\phi}} \; J_{cog}(s_g)

where

	oil-water surface tension		oil-gas surface tension
	oil-gas contact angle		oil-gas contact angle
	absolute permeability to air		porosity
	some function of water saturation		some function of gas saturation

The functions  and  are called Leverett J-functions. 

They are individual to every certain rock type, just like relative permeability curves.

There are many correlations for Leverett J-functions and the most popular is Brooks-Corey correlation:

J_{cow}(s_w) = a  \ ( s_{wn} )^{-1 / \lambda}

where

 – normalised water saturation,

 – critical water saturation,

 – model parameters which are set for laboratory data on capillary pressure and/or on resistivity water saturation during SHF.

Model parameter  is related to the the size of the pore size distribution.

The most popular value is 2 but it can vary to smaller or higher values.