Well control · Drilling
BOP Stack
A stack of large valves on top of the wellhead, under the rig floor, that can close the well if the crew loses control of formation fluids.
What it does
Closes the well, usually remotely with hydraulic actuators, so the crew can circulate the influx out and raise the mud weight before opening again. Annular preventers seal around any pipe; ram preventers seal on pipe or the open hole, and shear rams can cut drill pipe.
Basics
| Types | Annular, pipe rams, blind rams, shear rams |
| Actuation | Hydraulic, usually remote |
| Testing | Intervals set by risk, practice and regulation |
| Standard | API Standard 53 |
Common failures
- Failed pressure test or slow closing time
Troubleshooting
- Symptom
- Preventer does not hold test pressure
- Likely cause
- Worn packer or ram seals
- What to check
- Change the elements and retest before drilling ahead