Abstract: This invention provides improved geological formation evaluation, resulting in a more accurate prediction of the location of hydrocarbon. It also increases the yield at those sites. The disclosed method involves determination by a nuclear magnetic resonance tool of a downhole T2 distribution, determination of T2 cutoff valves at discrete points in the borehole, and deriving a variable T2 cutoff time by either linear or non-linear correlations. Derivation of these variable T2 cutoff times provides the likely location of high irreducible water saturation, even where large quantities of movable water reside nearby.