Simandoux (total shale) equation
Input(s)
\(\Phi_{e}\): Effective Porosity (fraction)
\(R_{t}\): Rock Resistivity (dimensionless)
\(R_{w}\): 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)
\[
S_{w}=\left(0.4 * \frac{R_{w}}{\Phi_{e}^{2}}\right) *\left(-\frac{V_{s h}}{R_{s h}}+\left(\left(\frac{V_{s h}}{R_{s h}}\right)^{2}+\left(\frac{5 *\left(\Phi_{e}\right)^{2}}{R_{w} * R_{t}}\right)\right)^{0.5}\right)
\]
Reference(s)
Bassiouni, Z., 1994, Theory, Measurement, and Interpretation of Well Logs. SPE Textbook Series Vol. 4. Chapter 1, Page: 16.