Productivity Index and Straight-Line IPR Calculator
Enter flow rate, reservoir pressure, and flowing bottomhole pressure. The calculator returns productivity index or related IPR values.
Calculation context and source notes
Productivity index relates stabilized liquid production rate to reservoir-to-wellbore pressure drawdown and defines a straight-line inflow-performance relationship for a producing well.
Use it for quick inflow estimates when the well response can be approximated by a linear productivity-index model. Establish PI from compatible stabilized rate and bottomhole-pressure data before forecasting another drawdown.
Solves for
J (STB/day/psi)
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Formula, variables, and sourceRelated source-backed guides
Formula, variables, and default calculation
Reproducible default result
With the default values shown below, the calculation returns J = 1 STB/day/psi. Defaults demonstrate the implementation; they are not recommended field values.
500
3000
2500
Input definitions
q_o
STB/dayOil Flow Rate
P_r
psiAverage Reservoir Pressure
P_wf
psiBottom-Hole Flowing Pressure
Output definitions
J
Productivity Index
q_o
Oil Flow Rate
P_r
Average Reservoir Pressure
P_wf
Bottom-Hole Flowing Pressure
Engineering use, assumptions, and limits
Use it for quick inflow estimates when the well response can be approximated by a linear productivity-index model. Establish PI from compatible stabilized rate and bottomhole-pressure data before forecasting another drawdown.
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.
Source and record status
Source metadata identifies the relationship implemented by the calculator. Check the cited edition, unit basis, and scope against the engineering case before operational use.
Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering. Productivity index and IPR.
Open source reference