\frac{1}{R_t} = \frac{\phi_e^m \, s_w^n}{A R_w (1-V_{sh})} + \frac{V_{sh}}{R_{sh}} s_w^{n/2} |
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 | ||
dimensionless constant, characterizing the rock matrix contribution to the total electrical resistivity | 0.5 ÷ 1, default value is 1 for sandstones and 0.9 for limestones | |
| 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 |