In oil and gas, a Christmas tree is an assembly of valves, spools, chokes and fittings mounted on top of the wellhead. Its job is to control and regulate the flow of hydrocarbons out of the well during production. The name comes from its branching, ornamented shape — a stack of valves and fittings that resembles a decorated tree.
An assembly of valves, chokes and fittings installed on the wellhead to control, regulate and monitor the flow of produced oil and gas from a completed well.
What the Christmas tree controls
Once a well is completed and ready to produce, the tree replaces the drilling blowout preventer on the wellhead. Through its master valves, wing valves and choke, operators can shut the well in, route flow to processing equipment, and throttle the production rate. The choke in particular lets operators manage pressure and flow precisely as reservoir conditions change.
The Christmas tree mounts on the wellhead but is a separate component. The wellhead anchors the casing and seals pressure; the tree controls production flow on top of it.
Surface and subsea trees
Trees come in two broad forms. Surface trees sit at ground level on land wells or on platform decks. Subsea trees sit on the seabed for offshore wells and are remotely operated, often in deep water. In both cases the function is the same: provide a controllable, monitored barrier through which produced fluids leave the well safely.
Because the tree is the primary interface between the reservoir and surface facilities, it integrates pressure and temperature monitoring, chemical injection points and safety shut-in systems.
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Frequently asked
It is an assembly of valves, spools, chokes and fittings mounted on the wellhead to control and regulate the flow of oil and gas during production.
The name comes from its branching, layered shape — a stack of valves and fittings that resembles a decorated tree.
The wellhead anchors the casing and provides pressure seals; the Christmas tree is a separate valve assembly mounted on the wellhead to control production flow.