Equivalent formation water resistivity from SP log

Input(s)

$\mathrm{R}_{\text {mfeq }}$: Equivalent Resistivity of Mud Filtrate (ohm m)

SSP: Static Spontaneous Potential (mV)

$\mathrm{T}$: Temperature $(\mathrm{F})$

Output(s)

$\mathrm{R}_{\text {weq: }}$: Equivalent Formation Water Resistivity (ohm m)

Formula(s)

$$ \mathrm{R}_{\mathrm{weq}}=(-61+0.133 * \mathrm{~T}) * \frac{\mathrm{R}_{\mathrm{mfeq}}}{10^{-\frac{\mathrm{SSP}}{61+0.133 * \mathrm{~T}}}} $$

Reference(s)

Core Laboratories. 2005. Formation Evaluation and Petrophysics, Page: 74.