Christmas Tree (oil and gas): What it is, How it Works

A Christmas tree is a device that controls flow from an oil or gas well. A Christmas tree is a series of valves, gauges, and chokes arranged vertically that are used to regulate flow control as well as inject fluids to stimulate production. A Christmas tree is called a Christmas tree because, if you have enough imagination, the combination of these components can resemble a Christmas tree. Some of the decorative valves on the Christmas tree are opened when the oil or gas well is ready for production and the processing and storage facilities are ready to receive it. Other decorative devices are used for pressure relief, monitoring, and injection of chemicals.

How it works

Christmas trees are used in oil exploration and production in both surface and underwater oil and gas wells. Christmas trees for surface wells are also called surface trees because they are connected to the wellhead visible at the well surface.

Christmas trees used for offshore drilling and production are called subsea trees. Subsea trees can be vertical or horizontal, depending on the design of the main valve (the valve set on the flow path and capable of shutting off production). Subsea trees are less similar to Christmas trees, but the name still exists today.

Wellhead vs. Christmas Tree

The Christmas tree is sometimes confused with the wellhead of an oil well. The Christmas tree sits on top of the wellhead, but it is a separate piece of equipment. There is no Christmas tree on the wellhead during drilling operations. Instead, a blowout preventer is installed on top of the wellhead while drilling and running casing/tubing. When the well is moved into production, the Christmas tree is installed to control flow. Therefore, the wellhead is there from the beginning, while the Christmas tree is an additional piece of equipment that comes into play when the well moves from the drilling phase to the production phase.