Fertl and Hammack equation
Input(s)
F: Formation Resistivity Factor (dimensionless)
\(\Phi_{e}\): Effective Porosity (fraction)
\(R_{t}\): Rock Resistivity (ohm m)
\(R_{w}\): Formation Water Resistivity (ohm m)
\(V_{s h}\): Bulk Volume Fraction of Shale (fraction)
\(R_{s h}\): Shale Resistivity (ohm m)
Output(s)
\(S_{w}\): Water Saturation (fraction)
Formula(s)
\[
S_{w}=\left(\frac{F * R_{w}}{R_{t}}\right)^{0.5}-\frac{V_{s h} * R_{w}}{0.4 * \Phi_{e} *\left(R_{s h}\right)}
\]
Reference(s)
Bassiouni, Z., 1994, Theory, Measurement, and Interpretation of Well Logs. SPE Textbook Series Vol. 4. Chapter 1, Page: 16.