Underground · Storage
Depleted Reservoir Storage
A former oil or gas reservoir reused to store natural gas: gas is injected in summer and withdrawn in winter through the old wells.
What it does
It is the most common type of underground gas storage because it reuses existing wells and pipelines. Part of the gas, the base or cushion gas, stays in the reservoir for good to keep pressure; the working gas above it is what the market uses. Deliverability is highest when the reservoir is full and falls as it empties.
Basics
| Most common type | Reuses wells and pipelines |
| Base gas | Permanent, keeps reservoir pressure |
| Working gas | Total capacity minus base gas |
| Cycle | Inject in summer, withdraw in winter |
Common failures
- Gas migrating out of the reservoir through old wells with poor cement
Troubleshooting
- Symptom
- Inventory does not balance with injection and withdrawal
- Likely cause
- Migration or a leaking old well
- What to check
- Survey old wells in the area and monitor pressure in observation wells