One f the SHF models:
| (1) | s_w(h) = 1 - a \exp \Big( -\Big(\frac{b}{h-h_{FWL}+c}\Big)^d \Big) |
where model parameters \{ a, \ b, \ c, \ d \} are calibrated on water saturation from OH logs for each lithofacies or petrotype individually.
The coefficient c is related to FWL and usually set the same for all lithofacies of a given reservoir unit.
If core data is abundant then one can build a reasonable correlation of model parameters on porosity and/or permeability:
| (2) | a = a(\phi), \; b = b(\phi), \; c = c(\phi) |