Downhole · Gas Lift
Production Tubing
The string that carries the produced fluids, lightened by the injected gas, to surface. The mandrels are part of it.
What it does
The injected gas lowers the density of the fluid inside it, cutting hydrostatic pressure so reservoir pressure can lift the liquid.
Basics
| Carries | Oil, water and gas, upward |
| Holds | Side pocket mandrels and valves |
| Size matters | Affects lift efficiency and critical velocity |
Common failures
- Liquid loading when gas velocity is too low
- Tubing leak that short circuits gas
Troubleshooting
- Symptom
- Casing and tubing pressures equalize
- Likely cause
- Tubing leak above the operating valve
- What to check
- Pressure test or leak detection survey