Pickett Crossplot Log True Resistivity Formula
Pickett Crossplot Log True Resistivity calculates base-10 logarithm of true rock resistivity for resistivity logs workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (S_w, R_w, phi, n, m) 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, log_Rt equals 0.758852 log10(ohm m).
0.6
0.1
0.22
2
2
Inputs
S_w
fractionWater Saturation
R_w
ohm mFormation Water Resistivity
phi
fractionPorosity
n
dimensionlessSaturation Exponent
m
dimensionlessCementation Exponent
Outputs
log_Rt
Base-10 Logarithm of True Rock Resistivity
R_t
True Rock Resistivity
S_w
Water Saturation
R_w
Formation Water Resistivity
phi
Porosity
n
Saturation Exponent
m
Cementation Exponent
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 13, Page 276.
Source