Reservoir EngineeringPermeability
Average Permeability in Radial Systems Formula
Average Permeability in Radial Systems calculates average permeability across radial zones for permeability workflows in reservoir engineering.
How engineers use this formula
Use this formula when the listed inputs (k_a, k_e, r_w, r_a, r_e) are known and the assumptions behind the cited permeability 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_avg equals 124.71725 mD.
k_amD
100
k_emD
200
r_wft
0.3
r_aft
10
r_eft
100
Inputs
k_a
mDPermeability between r_w and r_a
k_e
mDPermeability between r_a and r_e
r_w
ftWellbore radius
r_a
ftIntermediate radius between zones
r_e
ftDrainage radius
Outputs
k_avg
mD
Average permeability across radial zones
Source and review
reviewedSmith, Tracy & Farrar. Applied Reservoir Engineering Vol. 1, Equation 7-7.
Source