Wellhead
A wellhead is the pressure-containing surface assembly at the top of an oil or gas well that provides the structural and pressure interface to the casing strings and supports the <a href="/glossary/christmas-tree">Christmas tree</a> and other surface equipment.
Definition
Wellhead inspection covers casing-head pressures, seal integrity, body corrosion, and bolting condition. Subsea wellheads add ROV-deployed visual and UT inspection challenges.
What it is
The pressure-containing assembly at surface terminating the casing strings and supporting the tubing, providing the interface between the well and either the production tree or the drilling equipment.
Damage mechanisms in service
Inspection concerns pressure-containing components, load-bearing shoulders and sealing surfaces. Damage mechanisms include erosion at flow-wetted surfaces, sour service cracking where H2S is present, and fatigue at connections subject to vibration or thermal cycling.
Governing codes
API 6A for wellhead and christmas tree equipment; API 6D for valves; NACE MR0175 / ISO 15156 where the service is sour; API 570 where associated piping falls under inspection.
The common oversight
Inspecting the body and neglecting sealing and load shoulders. Those surfaces govern whether the assembly does its job, and they are the ones handling damages.
Where Wellhead fits in an inspection programme
A term is only useful when it connects to a decision. Wellhead appears in written procedures, in technique sheets, and in the records an owner or accreditation body reviews afterwards — which means the way it is defined in your documentation has to match the way it is applied on site. Where the two drift apart, audits find it. Atlantis writes and reviews procedures against the governing codes, trains inspection personnel to apply them, and builds the record-keeping that makes the evidence retrievable years later. Procedure development and code consulting · NDT training and certification · Ask us about your programme.
Related terms
- Christmas Tree — A Christmas tree is the vertical assembly of valves, fittings, and pressure gauges mounted on top of the wellhead that controls the flow of oil or gas from the well, named for its branching geometry.
- Blow-Out Preventer (BOP) — A blow-out preventer is a large, high-pressure valve stack installed at the wellhead during drilling and well intervention operations to seal, control, and monitor pressure to prevent the uncontrolled flow of formation fluids.
- Valve — A valve is a pressure-containing mechanical device that regulates, directs, or controls the flow of a fluid by opening, closing, or partially obstructing passageways, inspected by visual, MT/PT, UT, and pressure testing.
More asset-type terms
Pressure Vessel · Storage Tank · Heat Exchanger · Fired Heater · Pipeline · FPSO · Riser · Jacket · Topsides · Flange
Where this comes up in practice
Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.
Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.