PetrophysicsElectrical Properties
Static Spontaneous Potential from Equivalent Resistivities Formula
Static Spontaneous Potential from Equivalent Resistivities calculates static spontaneous potential for electrical properties workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (R_mfe, R_we, T_F) 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 -76.708463 mV.
R_mfeohm m
0.8
R_weohm m
0.1
T_F°F
180
Inputs
R_mfe
ohm mEquivalent Mud Filtrate Resistivity
R_we
ohm mEquivalent Formation Water Resistivity
T_F
°FFormation Temperature
Outputs
SSP
mV
Static Spontaneous Potential
K_sp
mV
SP Temperature Coefficient
R_mfe
ohm m
Equivalent Mud Filtrate Resistivity
R_we
ohm m
Equivalent Formation Water Resistivity
Source and review
reviewedAAPG Wiki. Water resistivity determination, SP method.
Source