Correlation between the initial formation water saturation s_{wi}, which is formed by the oil-water gravity segregation over time, and the height above FWL.
There is a fair number of various SHF mathematical models predicting the water saturation at a given point of a reservoir.
See also
Physics / Fluid Dynamics / Percolation
Petroleum Industry / Upstream / Subsurface E&P Disciplines / Field Study & Modelling
[ Petrophysics ] [ Basic reservoir properties ] [ SHF models ]