PetrophysicsRock Properties
Neutron Porosity in a Shaly Formation Formula
Neutron Porosity in a Shaly Formation calculates observed neutron porosity in a shaly formation for rock properties workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (Phi_T, V_sh, Phi_Nsh) 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_N equals 0.2475 fraction.
Phi_Tfraction
0.16
V_shfraction
0.25
Phi_Nshfraction
0.35
Inputs
Phi_T
fractionTrue Formation Porosity
V_sh
fractionShale Volume Factor
Phi_Nsh
fractionNeutron Porosity of Nearby Shale
Outputs
Phi_N
fraction
Observed Neutron Porosity in a Shaly Formation
Phi_T
fraction
True Formation Porosity
V_sh
fraction
Shale Volume Factor
Phi_Nsh
fraction
Neutron Porosity of Nearby Shale
Source and review
reviewedCore Laboratories. 2005. Formation Evaluation and Petrophysics, Page 108.
Source