PetrophysicsRock Properties
NMR Free-Fluid Index from Porosity Partition Formula
NMR Free-Fluid Index from Porosity Partition calculates free-fluid index for rock properties workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (MPHI, 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, FFI equals 0.16 fraction.
MPHIfraction
0.24
BVIfraction
0.08
Inputs
MPHI
fractionNMR Effective Porosity
BVI
fractionBulk Volume Irreducible
Outputs
FFI
fraction
Free-Fluid Index
MPHI
fraction
NMR Effective Porosity
BVI
fraction
Bulk Volume Irreducible
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, Chapter 1.
Source