RQI=0.0314 \, \sqrt{\frac{k}{\phi_e - \phi_0}}

where 

absolute permeability to air, md

effective porosity

porosity cut-off


Unit = μm

This value accounts for monotonous growth of permeability on porosity and the square root decreases the variability thus increasing linearity of correlation between RQI and porosity (usually normalised porosity, see Flow Zone Indicator (FZI)). 


See also


Petroleum Industry / Upstream / Subsurface E&P Disciplines / Petrophysics

Flow Zone Indicator (FZI) ] [ Absolute permeability @model ]