One of the saturation from resistivity models: --------- where constant
A is defined by formation shaliness
V_{sh}: where
s_w
\phi_e
V_{sh}
R_t
R_w
R_{sh}
m
n 1.5 ÷ 2.5, default value is 2
(1)
s_w = \left[ \frac{\sqrt{\frac{1}{R_t}}}{ 1 + \sqrt{ \frac{1}{23}}} \right]^{\, (2/n)}
(2)
\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}
\frac{1}{A} = 1 + \Big( \frac{V_{sh}^{2-V_{sh}}}{\phi_e} \, \frac{R_w}{R_{sh}} \Big)^{1/2}
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
See Also
Petroleum Industry / Upstream / Subsurface E&P Disciplines / Petrophysics
Well & Reservoir Surveillance / Well logging / Reservoir Data Logs (RDL) / Formation Resistivity Log @model