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Well Log Petrophysics Calculator

Calculate Vshale, water saturation (Sw), bulk volume water (BVW), hydrocarbon saturation (Sh), and pay/non-pay classification from basic log data.

Gamma Ray & Shale Volume

GR Reading (API)

GR Clean (API)

GR Shale (API)

Vsh Cutoff (fraction)

Rt — True Resistivity (ohm-m)

Rw — Water Resistivity (ohm-m)

Porosity (fraction)

a — Tortuosity Factor

m — Cementation Exponent

n — Saturation Exponent

Sw Cutoff (fraction)

Porosity Cutoff (fraction)

Vshale (IGR)

Water Saturation (Sw)

Hydrocarbon Sat. (Sh)

Bulk Volume Water (BVW)

Formation Factor (F)

Pay Flag

How this works

Vshale: IGR = (GR - GR_clean) / (GR_shale - GR_clean). Linear gamma ray index.

Sw: Archie equation: Sw = (a * Rw / (phi^m * Rt))^(1/n).

BVW: Bulk Volume Water = Sw * Porosity. At irreducible if BVW < 0.035.

Pay: Zone is PAY if Vsh < Vsh cutoff AND Sw < Sw cutoff AND Phi > Phi cutoff.

Need help with petrophysical evaluation or log interpretation across multiple wells?