Downhole · Gas Lift
Unloading Valves
Gas lift valves set at several depths above the operating valve, used mainly to start the well.
What it does
Lighten the fluid column step by step during kickoff, so injection can work down to the deepest valve. Once the well unloads they close.
Basics
| Used for | Kickoff, also called unloading |
| Common type | Injection pressure operated (open on casing pressure) |
| Other type | Production pressure operated (open on tubing fluid pressure) |
| Flow | One way, annulus to tubing, through a check |
Common failures
- Valve stays open after unloading, gas injected too shallow
- Leaking check lets fluid back into the annulus
Troubleshooting
- Symptom
- Injection depth shallower than design
- Likely cause
- Upper valve not closing
- What to check
- Pressure survey or temperature log to find the injection point