PetrophysicsResistivity Logs
Partially Saturated Shaly Sand Resistivity Vsh Model Formula
Partially Saturated Shaly Sand Resistivity Vsh Model calculates partially saturated shaly-sand resistivity for resistivity logs workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (S_w, R_w, V_sh, R_sh, F) 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, R_t equals 2.657807 ohm m.
S_wfraction
0.7
R_wohm m
0.08
V_shfraction
0.25
R_shohm m
2.5
Fdimensionless
20
Inputs
S_w
fractionWater Saturation
R_w
ohm mFormation Water Resistivity
V_sh
fractionBulk Volume Fraction of Shale
R_sh
ohm mShale Resistivity
F
dimensionlessFormation Resistivity Factor
Outputs
R_t
ohm m
Partially Saturated Shaly-Sand Resistivity
inv_R_t
1/(ohm m)
Partially Saturated Shaly-Sand Conductivity
Source and review
reviewedBassiouni, Z. 1994. Theory, Measurement, and Interpretation of Well Logs. SPE Textbook Series Vol. 4, Chapter 1, Page 16.
Source