Wellhead
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It has been suggested that Christmas tree (oil well) be merged into this article or section. (Discuss) |
A wellhead is a general term used to describe the component that is used to suspend casing strings and provide sealing functionality for oil wells. Wellheads can be located on oil platforms, subsea or onshore. A wellhead system provides the following basic functionality: support of the casing and tubing strings (the tubing string may also be suspended in the Christmas tree; providing a seal between the different strings; allowing for access to annuli between the different casing/tubing strings.
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[edit] Components
The primary components of a wellhead system are:
- casing head
- casing spools
- casing hangers
- packoffs and isolation seals
- bowl protectors
- test plugs
- mudline suspension systems
- tubing heads
- tubing hangers
- tubing head adapters
[edit] Specification
The basic requirements for materials, dimensions, test procedures and pressure ratings for wellheads and wellhead equipment are defined on API Spec 6A: Specification for Wellhead and Christmas Tree Equipment. Wellheads are cemented in place and are generally permanently kept in place, although in exploration wells they may be recovered for use again.
[edit] Design factors
Wellheads are manufactured in a vast variety of manners for numerous purposes which dictate design. Factors that affect wellhead configuration are pressure, temperature, location, well depth, well size, well purpose, expected well life, well control equipment interface, drilling method, etc.
[edit] Functions
A wellhead serves numerous functions. Some of these are:
- Means of casing suspension. (Casing is the permanently installed pipe used to line the well hole for pressure containment, collapse prevention, etc.)
- Means of casing pressure isolation when multiple casing strings are used
- Means of attaching a blowout preventer during drilling
- Means of attaching a tree for well control during production, injection, or other operations
- Means of well access
- Means of pump attachment
- Means of tubing suspension (Tubing is removable pipe installed in the well)
[edit] See also
[edit] External links
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