Relationship between SSP and Rw for water containing salts (non-NaCl predominant)

Input(s)

$a_{N a}$: Activity of $\mathrm{Na}$ Ions in Water (dimensionless)

$\mathrm{K}$: Equilibrium Constant $(\mathrm{mV})$

$a_{C a}$: Activity of $\mathrm{Ca}$ Ions in Water (dimensionless)

$a_{M g}$: Activity of $\mathrm{Mg}$ Ions in Water (dimensionless)

$a_{\text {Nam }}$: Activity of $\mathrm{Na}$ Ions in Mud Filtrate (dimensionless)

$a_{\text {Cam }}$: Activity of $\mathrm{Ca}$ Ions in Mud Filtrate (dimensionless)

$a_{M g m}$: Activity of $\mathrm{Mg}$ Ions in Mud Filtrate (dimensionless)

Output(s)

$E_{s p p}$: Static Self Potential (V)

Formula(s)

$$ E_{s s p}=-K * \log \left(\frac{\left(a_{N a}+\left(a_{C a}+a_{M g}\right)^{0.5}\right)}{\left(a_{N a m}+\left(a_{C a m}+a_{M g m}\right)^{0.5}\right)}\right) $$

Reference(s)

Bassiouni, Z., 1994, Theory, Measurement, and Interpretation of Well Logs. SPE Textbook Series Vol. 4. Chapter 6, Page: 135.