PetrophysicsElectrical Properties
Archie Resistivity Index from Water Saturation Formula
Archie Resistivity Index from Water Saturation calculates resistivity index for electrical properties workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (S_w, n) 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, RI equals 4 dimensionless.
S_wfraction
0.5
ndimensionless
2
Inputs
S_w
fractionWater Saturation
n
dimensionlessSaturation Exponent
Outputs
RI
dimensionless
Resistivity Index
S_w
fraction
Water Saturation
n
dimensionless
Saturation Exponent
Source and review
reviewedSLB Energy Glossary. Resistivity index.
Source