Christmas tree

(Welcome corrections/additions by experts in the field)

Christmas tree (in engineering) is the name given to the petroleum well outlet configuration.

Why the name[]

On shore[]

The well outlet is connected with branches of various sizes incorporating suitable valves and fittings on every branch for sending the output from the well to different destinations. The cluster of valves and fittings of different sizes standing erect appears similar to a Christmas tree: hence the name.

Off shore[]

The term "Christmas Tree" has now become something of a misnomer as complexity has increased and they are more frequently manufactured from a single block of steel rather than made from multiple flanged joints. Especially in subsea applications the resemblance no longer exists given the frame and support systems into which the main valve block is integrated. It is also more usual now to call it either "Subsea Tree" or "Surface Tree".

Operation requirement[]

The oil or gas well after drilling has to be suitably controlled to regulate the flow. The well pressure generally is very high, of the order of about 50 Atm.

The well head itself will have a valve to control the main output of the well and also all the other branches above that point. This control can also be used for admission of water or other fluids when the yield goes down.

Safety requirements[]

Fittings[]

All the fittings on the Christmas tree are of flanged connection as welding is not allowed on these pipes and fittings due to the explosive nature of the well fluid output.

Area protection[]

The area surrounding the well head is cordoned off by a fence with facility for the operating staff only to enter for operation purposes only.

No smoking is allowed in this protected area.