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.