| FZI = \frac{RQI}{\phi_r} |
where
RQI | Rock Quality Index |
\phi_r | normalised porosity |
It has much weaker dependence on effective porosity and shaliness and can be often considered constant within a given lithofacies which makes it a very efficient tool for lithofacies analysis
The constant FZI means that permeability strictly follows Cozeny-Karman permeability @model.
The FZI depends on grains size distribution, shape and packing.
The most popular correlation with a mean grain size D_g is given as:
| (1) | FZI = a \cdot D_g |
where coefficient a is a function of grain shape, packing, inter-grain clay and, as a consequence, of inter-grain effective porosity \phi.
See also
Petroleum Industry / Upstream / Subsurface E&P Disciplines / Petrophysics