Analysis · Well Testing
IPR & Productivity Index
The productivity index is the oil rate per unit of pressure drawdown. The inflow performance relationship (IPR) is the curve of rate against flowing bottomhole pressure.
What it does
Tells how much the well can deliver at each bottomhole pressure. A constant productivity index only holds for single phase flow; below the bubble point other methods such as Vogel's two phase IPR are used.
Basics
| PI units | STB/D per psi |
| Constant PI | Single phase flow only |
| Two phase | Vogel IPR |
| Gas wells | Deliverability tests, AOF |
Common failures
- Straight line PI applied to a well below the bubble point overstates its inflow
Troubleshooting
- Symptom
- Well delivers less than the PI predicted
- Likely cause
- Two phase flow below the bubble point
- What to check
- Rebuild the IPR with Vogel from a new test