PetrophysicsRock Properties
Relation Between Concentration of K Th or U and Recorded Total Gamma Ray Signal Formula
Relation Between Concentration of K Th or U and Recorded Total Gamma Ray Signal calculates total gamma ray signal for rock properties workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (C_Th, C_U, C_K) are known and the assumptions behind the cited rock 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, gamma equals 37.5 API units.
C_Thppm
5
C_Uppm
2
C_Kwt%
1.5
Inputs
C_Th
ppmThorium Concentration
C_U
ppmUranium Concentration
C_K
wt%Potassium Concentration
Outputs
gamma
API units
Total Gamma Ray Signal
C_Th
ppm
Thorium Concentration
C_U
ppm
Uranium Concentration
C_K
wt%
Potassium Concentration
Source and review
reviewedBassiouni, Z. 1994. Theory, Measurement, and Interpretation of Well Logs. SPE Textbook Series Vol. 4, Chapter 7, Page 152.
Source