Coates NMR Permeability from Free-Fluid Ratio Formula
Coates NMR Permeability from Free-Fluid Ratio calculates nmr-derived permeability by coates model for rock properties workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (phi_NMR, C, FFI, BVI) 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, k_NMR equals 71.7409 mD.
0.22
0.1
0.14
0.08
Inputs
phi_NMR
fractionNMR Porosity
C
dimensionlessCoates Empirical Porosity Constant
FFI
fractionFree-Fluid Index
BVI
fractionBulk Volume Irreducible
Outputs
k_NMR
NMR-Derived Permeability by Coates Model
FFI
Free-Fluid Index
BVI
Bulk Volume Irreducible
C
Coates Empirical Porosity Constant
phi_NMR
NMR Porosity
Source and review
reviewedNMR Logging Principles and Applications, Coates, G.R., Xiao, L., Prammer, M.G. (1999)
Coates, G.R., Xiao, L., and Prammer, M.G. 1999. NMR Logging Principles and Applications. Halliburton Energy Services, MPERM glossary entry.
Source