Rig · Drilling
Mast & Substructure
The steel structure that holds the crown block and the drill string, standing on the substructure that supports it and the rig floor.
What it does
Carries the hook load: the weight of the string, collars and equipment on the hook, reduced by mud buoyancy and wall friction. Land rig masts are laid down when the rig moves; derricks are assembled piece by piece.
Basics
| Mast | Rectangular or trapezoidal, laid down to move |
| Derrick | Pyramidal, assembled piece by piece |
| Substructure | Supports the mast and rig floor |
Common failures
- Hook load beyond what the structure is designed for
Troubleshooting
- Symptom
- Hook load higher than expected while pulling out
- Likely cause
- Wall friction or tight hole
- What to check
- Work the pipe and review hole conditions before pulling harder