IPR Calculator (Inflow Performance Relationship)
Calculate and plot IPR curves using Vogel, Darcy, Composite, or Fetkovich models. Find AOF, operating points, and depletion sensitivity.
Input Parameters
Quick Lookup
Operating Point Table
| Pwf (psi) | Pwf / Pr | q (bbl/d) | % of AOF |
|---|
How this was calculated
Models used:
- Vogel (1968): q/qmax = 1 - 0.2(Pwf/Pr) - 0.8(Pwf/Pr)² — for saturated oil reservoirs below bubble point
- Darcy/PI: q = J × (Pr - Pwf) — for single-phase flow above bubble point
- Composite (Standing): Linear above Pb, Vogel below Pb
- Fetkovich (1973): q = C × (Pr² - Pwf²)ⁿ — empirical, 0.5 ≤ n ≤ 1.0
Assumptions: Steady-state or pseudo-steady-state flow. Single-phase or two-phase (oil + gas). No water coning. Vertical well with uniform drainage. Skin = 0 (not explicitly modeled).
When not to trust this: Horizontal wells (use Joshi/Babu-Odeh), fractured wells (use bilinear/linear flow models), gas wells (use Rawlins-Schellhardt), or wells with significant skin/damage. Actual well test data should validate the IPR.
Run a calculation to see your well's inflow performance. Composite and depletion analyses can reveal hidden production potential.
Book a free strategy call →What is an IPR Curve?
The Inflow Performance Relationship (IPR) is one of the most fundamental concepts in petroleum production engineering. It describes the relationship between a well's flowing bottomhole pressure (Pwf) and the corresponding liquid production rate (q). Every petroleum engineer, from students to VPs of production, needs to understand IPR curves to properly design artificial lift systems, optimize well performance, and forecast production.
An IPR curve plots flowing bottomhole pressure on the y-axis versus flow rate on the x-axis. The curve starts at reservoir pressure (Pr) where flow rate is zero (the well is shut in) and ends at an Absolute Open Flow (AOF) rate where flowing pressure theoretically reaches zero. The shape of the curve depends on whether the well is producing above or below the bubble point pressure and on reservoir and fluid properties.
When to Use Each Model
Vogel's correlation (1968) is the most widely used IPR model for solution-gas drive reservoirs producing below the bubble point. It assumes that two-phase flow (oil and gas) causes a curved, non-linear IPR. Vogel showed that a single dimensionless equation can approximate the IPR for a wide range of saturated oil wells. Use Vogel when reservoir pressure is at or below bubble point and the primary drive mechanism is dissolved gas.
Darcy / PI (Productivity Index) applies when the well produces single-phase liquid above the bubble point. In this case, the relationship between pressure drawdown and rate is linear: q = PI x (Pr - Pwf). The PI model is simple but only valid while the flowing pressure stays above the bubble point.
Composite (Standing's extension) combines both models. Above the bubble point the IPR is linear (Darcy), and below the bubble point it follows a modified Vogel curve. This is the most realistic model for reservoirs where the static pressure is above bubble point but drawdown may take flowing pressure below it. Many real-world wells operate in this regime.
Fetkovich's method (1973) is an empirical approach that uses a multi-rate test to determine an exponent n between 0.5 and 1.0. When n = 1.0, Fetkovich reduces to a simplified Vogel-like curve. When n = 0.5, it represents a high-turbulence, rate-dependent skin scenario. Fetkovich is especially useful when you have multi-rate test data and want to capture non-Darcy flow effects.
How to Use This Calculator
Select your IPR model, enter the required reservoir and test data, and click Calculate IPR. The tool plots the full IPR curve, annotates the Absolute Open Flow (AOF), and generates an operating point table at key pressure fractions. Enable depletion sensitivity to see how the IPR shifts as reservoir pressure declines over time. Use the Quick Lookup panel to find the flow rate at any given flowing pressure, or the required flowing pressure to achieve a target rate. This calculator runs entirely in your browser with no data sent to any server.