Wellhead
A wellhead is the pressure-containing surface equipment installed at the top of an oil or gas well that suspends and seals the casing and tubing strings and provides the interface for drilling and production equipment. Its components include the casing head, casing spools, casing hangers, tubing head and tubing hanger, with side outlets and valves for annulus monitoring and access. During drilling it supports the blowout preventer stack; after completion the Christmas tree is mounted on top of it. Surface wellhead equipment is designed and manufactured to API Spec 6A (ISO 10423). Selection parameters include rated working pressure (API 6A ratings range from 2,000 to 20,000 psi), temperature class, material class for sour service according to NACE MR0175 / ISO 15156, product specification level (PSL), performance requirement (PR) and end connections.
Examples
- Conventional spool-type wellhead for an onshore oil well
- Compact multi-bowl wellhead for faster drilling operations
- Sour-service wellhead with material class for H2S environments