s_w = \left[ \frac{\sqrt{\frac{1}{R_t}}}{ \frac{V_{sh}^{\left( 1-0.5 \, V_{sh} \right)}}{\sqrt{R_{sh}}} + \sqrt{ \frac{\phi_e^m}{A \, R_w}}} \right]^{\, (2/n)} |
where
| formation water saturation | ||
| effective porosity | ||
| shaliness | ||
| specific electrical resistivity from OH logs | ||
| specific electrical resistivity of formation water | ||
| specific electrical resistivity of wet shales | ||
| formation matrix cementation exponent | 1.5 ÷ 2.5, default value is 2 | |
| formation matrix water-saturation exponent | 1.5 ÷ 2.5, default value is 2 |