The tubing hanger is the part of the wellhead that holds the production tubing. It sits in the bowl of the tubing head spool, directly below the tubing head adapter and the Christmas tree. It is small, but it is one of the most important seals in the well.
What a tubing hanger does
- Carries the tubing weight. The full string, and everything run on it, hangs from the hanger.
- Seals the annulus. Seals on the hanger’s outside diameter isolate the tubing-casing annulus from the tree above.
- Provides a barrier profile. An internal thread or profile lets a back-pressure valve or two-way check valve be set, so the tree can be removed safely and a BOP installed.
- Passes control lines. Ports carry hydraulic lines for the subsurface safety valve and cables for downhole gauges through the hanger.
How it is installed
The hanger is made up to the top of the tubing string and run through the BOP. It lands on the taper of the tubing head bowl. Lockdown screws in the spool are then run in to hold it down, because pressure from below or thermal growth of the tubing can push it upwards. The BOP is removed and the tubing head adapter and tree go on top.
Common hanger types
- Mandrel type: the standard. A threaded solid body, usually with an extended neck that seals into the tubing head adapter.
- Wrap-around: clamps around the tubing; used in some workover and dual completions.
- Dual hangers: two tubing strings, each with its own bore, for dual completions.
The tubing head adapter
The adapter connects the tubing head spool to the tree, often reducing from the spool’s top flange, such as 11 in, to the tree’s bore, such as 7-1/16 in or 3-1/16 in. On many designs the hanger neck seals inside the adapter, adding a second seal between well pressure and the outside world.
What goes wrong
- Seal damage from running through a rough BOP bore.
- Lockdown screws not fully run in, allowing the hanger to lift.
- Control line ports leaking after repeated connections.
- Corrosion of the BPV thread, making it hard to set a barrier during workover.
Frequently asked questions
Is the tubing hanger part of the tree?
No. It is part of the wellhead. The tree starts at the tubing head adapter, though they are designed to work together.
Why is a back-pressure valve needed?
It plugs the tubing bore so pressure is contained while the tree is replaced by a BOP or the other way round.
See how the whole stack fits together in Wellhead vs Christmas Tree.
Work with RAPID GLOBAL
RAPID GLOBAL designs, analyses and requalifies wellhead, subsea and valve equipment to API standards. If you need help with tubing hanger or wellhead design, talk to an engineer.
