Production EngineeringInflow Performance
Productivity Index and Straight-Line IPR Formula
Productivity index relates liquid production rate to drawdown for straight-line inflow performance in a producing well.
How engineers use this formula
Use it for quick inflow estimates when the well response can be approximated by a linear PI model.
Assumptions
- The pressure-rate relationship is linear over the evaluated range.
- Reservoir and flowing bottomhole pressures are representative.
- Rate and pressure units match the formula constants used.
Limitations
- May underrepresent nonlinear two-phase behavior.
- Does not include tubing, choke, artificial lift, or surface constraints.
Common mistakes
- Using wellhead pressure instead of flowing bottomhole pressure.
- Applying a straight-line PI model to strongly nonlinear inflow.
- Mixing liquid-rate units.
Default example
Using the default inputs, J equals 1 STB/day/psi.
q_oSTB/day
500
P_rpsi
3000
P_wfpsi
2500
Inputs
q_o
STB/dayOil Flow Rate
P_r
psiAverage Reservoir Pressure
P_wf
psiBottom-Hole Flowing Pressure
Outputs
J
STB/day/psi
Productivity Index
q_o
STB/day
Oil Flow Rate
P_r
psi
Average Reservoir Pressure
P_wf
psi
Bottom-Hole Flowing Pressure
Source and review
reviewedAhmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering. Productivity index and IPR.
Source