Membrane Potential for SP Log Formula
Membrane Potential for SP Log calculates membrane potential for electrical properties workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (R_gas, T_a, F_faraday, a_1, a_2) are known and the assumptions behind the cited electrical properties relationship match the engineering case being checked.
Assumptions
- Input values are representative for the well, reservoir, fluid, or equipment case being evaluated.
- The declared units match the field-unit constants used in the formula.
- The cited formula applies to the selected petroleum engineering workflow.
Limitations
- The calculation does not replace a full engineering model or operating procedure.
- Accuracy depends on the source correlation, assumptions, input quality, and unit consistency.
Common mistakes
- Mixing unit systems without converting the inputs.
- Using default example values as field recommendations.
- Applying the formula outside the source assumptions.
Default example
Using the default inputs, E_m equals 0.048539 V.
8.314
350
96485.336
0.25
0.05
Inputs
R_gas
J/mol/KUniversal Gas Constant
T_a
KAbsolute Temperature
F_faraday
C/molFaraday Constant
a_1
dimensionlessActivity on Side 1
a_2
dimensionlessActivity on Side 2
Outputs
E_m
Membrane Potential
R_gas
Universal Gas Constant
T_a
Absolute Temperature
F_faraday
Faraday Constant
a_1
Activity on Side 1
a_2
Activity on Side 2
Source and review
reviewedTheory, Measurement, and Interpretation of Well Logs, Bassiouni, Z. (1994)
Bassiouni, Z. 1994. Theory, Measurement, and Interpretation of Well Logs. SPE Textbook Series Vol. 4, Chapter 6, Page 131.
Source