Production EngineeringInflow Performance
Productivity Index for a Gas Well Formula
Productivity Index for a Gas Well calculates gas-well productivity index for inflow performance workflows in production engineering.
How engineers use this formula
Use this formula when the listed inputs (k, h, T, A, C_A, r_w, S) are known and the assumptions behind the cited inflow performance 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, J_g equals 0.000188 MSCF/day/psi2/cP.
kmD
50
hft
40
TdegR
600
Aft2
4356000
C_Adimensionless
31.6
r_wft
0.328
Sdimensionless
5
Inputs
k
mDPermeability
h
ftPay Thickness
T
degRReservoir Temperature
A
ft2Drainage Area
C_A
dimensionlessShape Factor
r_w
ftWellbore Radius
S
dimensionlessSkin Factor
Outputs
J_g
MSCF/day/psi2/cP
Gas-Well Productivity Index
k
mD
Permeability
h
ft
Pay Thickness
Source and review
reviewedAhmed, T. and McKinney, P.D. 2005. Advanced Reservoir Engineering. Gulf Publishing / Elsevier, Chapter 3, Page 188.
Source