Before · Abandonment
Cement Bond Log
A sonic log run inside the casing that shows how well the cement is bonded to the outside of the pipe.
What it does
Tells the crew where the cement sheath can be trusted as a barrier and where it cannot. Alberta requires a cement evaluation log when the calculated cement top is too close to the uppermost porous zone, or when vent flow or gas migration is present.
Basics
| Tool | Sonic transmitter and receivers on wireline |
| Newer logs | 360 degree view of the cement |
| Required when | Cement top less than 15 m above the uppermost porous zone, or SCVF or gas migration (Alberta) |
Common failures
- Reading a microannulus as bad cement, or missing a narrow channel
Troubleshooting
- Symptom
- Log shows poor bond over a zone
- Likely cause
- Channel or microannulus
- What to check
- Repeat under pressure or use a 360 degree tool before deciding the repair