Relationship Between SSP and Rw - NaCl Predominant Formula
Relationship Between SSP and Rw - NaCl Predominant calculates static self potential for electrical properties workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (R_mfeq, K_sp, A_rw, a_w) 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, SSP equals -57.673612 mV.
0.8
70
0.12
1
Inputs
R_mfeq
ohm mEquivalent Mud Filtrate Resistivity
K_sp
mVSP Equilibrium Constant
A_rw
ohm mFormation-Water Activity Proportionality Factor
a_w
dimensionlessNaCl Activity in Formation Water
Outputs
SSP
Static Self Potential
R_weq
Equivalent Formation Water Resistivity
R_mfeq
Equivalent Mud Filtrate Resistivity
K_sp
SP Equilibrium Constant
A_rw
Formation-Water Activity Proportionality Factor
a_w
NaCl Activity in Formation Water
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 133.