Christmas tree

In petroleum and natural gas extraction, a Christmas tree, or “tree,” is an assembly of a multi-valved structure consisting of valves, pipe spools, and fittings used to control the flow of oil from the well.  The shape of the wellhead structure with valves looks like a pine tree, so the wellhead is called a “Christmas tree”. The Christmas Tree is connected to the top of the tubing and cemented to the top of the casing. These valves regulate pressure, control flow, and allow access to the wellbore when further completion work is required. From the outlet valve of the Christmas Tree, the flow can be connected to a distribution network of pipelines and tanks to distribute the product to refineries, natural gas compressor stations, or oil export terminals.

The Christmas tree consists of an assembly of a gate valve that controls the flow of hydrocarbons. It may consist of individual valves bolted together, or it may feature a cast or forged steel solid block into which the valve chests are machined. Occasionally it is a combination of the two. In all cases, the valve seats and gates are removable for replacement or repair

The Function of a Christmas Tree

The primary function of a Christmas tree is to manage the flow of oil and gas from the well. It serves several key purposes:

• Flow Control: Regulating the flow rate of oil and gas to optimize production.
• Pressure Management: Maintaining appropriate pressure levels within the well to prevent blowouts.
• Separation of Fluids: Allowing for the separation of oil, gas, and water as they are extracted.
• Safety Measures: Providing emergency shut-off capabilities to prevent uncontrolled releases of hydrocarbons.

In producing wells, injection of chemicals, alcohols, or oil distillates to prevent or solve production problems (such as blockages) may be used.

Components of a Christmas Tree

A typical Christmas tree is composed of a master gate valve, a pressure gauge, a wing valve, a swab valve, and a choke as shown in Fig. 1. The Christmas tree may also have a number of check valves.

At the bottom, we find the casing head and casing hangers. The casing will be screwed, bolted, or welded to the hanger. Several valves and plugs will normally be fitted to give access to the casing. This will permit the casing to be opened, closed, bled down, and, in some cases, allow the flowing well to be produced through the casing as well as the tubing. The valve can be used to determine leaks in the casing, tubing, or packer, and will also be used for lift gas injection into the casing.

The tubing hanger (also called a donut) is used to position the tubing correctly in the well. Sealing also allows Christmas tree removal with pressure in the casing.

Our wellhead experience includes:

• Conventional stack-up wellhead systems that use mandrel casing hangers or slip-and-seal casing hangers
• Full-bore and slim-hole multi-bowl style casing head systems for drill-through system technologies, which utilise primary mandrel hangers and pack off for casing support with contingency slip-and-seal casing hangers
• Systems for gas and oil well applications, fully design-approved for use with both on- and offshore installations
• A range of starter head options: weld-on, screw-on and no-weld slip-lock connectors.