PetrophysicsResistivity Logs
Simandoux Total Shale Equation Formula
Simandoux Total Shale Equation calculates water saturation for resistivity logs workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (R_w, phi_e, V_sh, R_sh, R_t) are known and the assumptions behind the cited resistivity logs 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, S_w equals 0.226188 fraction.
R_wohm m
0.08
phi_efraction
0.22
V_shfraction
0.15
R_shohm m
3
R_tohm m
20
Inputs
R_w
ohm mFormation Water Resistivity
phi_e
fractionEffective Porosity
V_sh
fractionVolume of Shale
R_sh
ohm mShale Resistivity
R_t
ohm mTrue Formation Resistivity
Outputs
S_w
fraction
Water Saturation
R_t
ohm m
True Formation Resistivity
R_sh
ohm m
Shale Resistivity
Source and review
reviewedSimandoux total shale equation, PetroleumEngineers.Net
PetroleumEngineers.Net formula page. Simandoux total shale equation.
Source