\frac{1}{R_t} = \frac{\phi_e^m \, s_w^n }{A R_w} \quad \Rightarrow \quad s_w = \Big ( \frac{A}{\phi_e^m} \; \frac{R_w}{R_t} \Big) ^{1/n} |
where constant is defined by formation shaliness
:
\frac{1}{A} = 1 + \Big( \frac{V_{sh}^{2-V_{sh}}}{\phi_e} \, \frac{R_w}{R_{sh}} \Big)^{1/2} |
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 |