PetrophysicsRock Properties
Gas-Effect Corrected Porosity from Neutron-Density Logs Formula
Gas-Effect Corrected Porosity from Neutron-Density Logs calculates corrected porosity for gas effect for rock properties workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (Phi_D, Phi_N) 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, Phi_corr equals 0.152971 fraction.
Phi_Dfraction
0.18
Phi_Nfraction
0.12
Inputs
Phi_D
fractionDensity Porosity
Phi_N
fractionNeutron Porosity
Outputs
Phi_corr
fraction
Corrected Porosity for Gas Effect
Phi_D
fraction
Density Porosity
Phi_N
fraction
Neutron Porosity
Source and review
reviewedCore Laboratories. 2005. Formation Evaluation and Petrophysics, Page 111.
Source