Wellbore · Drilling
Casing & Cement
Strings of steel pipe run into the hole in stages and cemented in place.
What it does
Keeps the hole from caving in, isolates formations to prevent crossflow, protects fresh water zones and anchors the BOP and downhole equipment. Usual order: conductor, surface, intermediate and production casing.
Basics
| Conductor | First, short and wide, holds shallow soil |
| Surface casing | Protects fresh water aquifers, carries the BOP |
| Intermediate | Isolates weak or high pressure zones |
| Production casing | Set across the reservoir |
Common failures
- Zones not isolated behind the casing
Troubleshooting
- Symptom
- Fluid communicating between zones behind casing
- Likely cause
- Isolation failed
- What to check
- Evaluate the cement and plan a remedial cement job