PetrophysicsRock Properties
Epithermal Neutron Diffusion Coefficient Formula
Epithermal Neutron Diffusion Coefficient calculates epithermal diffusion coefficient for rock properties workflows in petrophysics.
How engineers use this formula
Use this formula when the listed inputs (xi, L_e, Sigma_e) 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, D_e equals 10 dimensionless.
xidimensionless
0.5
L_ecm
10
Sigma_e1/cm
0.2
Inputs
xi
dimensionlessLogarithmic Energy Decrement per Collision
L_e
cmSlowing-Down Length
Sigma_e
1/cmMacroscopic Scattering Cross Section
Outputs
D_e
dimensionless
Epithermal Diffusion Coefficient
xi
dimensionless
Logarithmic Energy Decrement per Collision
L_e
cm
Slowing-Down Length
Sigma_e
1/cm
Macroscopic Scattering Cross Section
Source and review
reviewedBassiouni, Z. 1994. Theory, Measurement, and Interpretation of Well Logs. SPE Textbook Series Vol. 4, Chapter 2, Page 40.
Source