PetrophysicsRock Properties
Fraction of Total Porosity Occupied by Clays Formula
Fraction of Total Porosity Occupied by Clays calculates fraction of total porosity occupied by clays for rock properties workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (Phi_S, Phi_D) 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, q equals 0.2 fraction.
Phi_Sfraction
0.3
Phi_Dfraction
0.24
Inputs
Phi_S
fractionSonic Log Porosity
Phi_D
fractionDensity Log Porosity
Outputs
q
fraction
Fraction of Total Porosity Occupied by Clays
Phi_S
fraction
Sonic Log Porosity
Phi_D
fraction
Density Log Porosity
Source and review
reviewedCore Laboratories. 2005. Formation Evaluation and Petrophysics, Page 98.
Source