The document describes several key components of a Christmas tree used in oil and gas production: - Master valves control all flow from the wellbore, with most trees having two for redundancy. The upper valve is used routinely and the lower provides backup. - Pressure gauges monitor well pressure, now often using electronic gauges to transmit data for remote monitoring. - Wing valves control or isolate production flow to surface facilities, with some trees having two - one main and one backup. Others use one for production and another as a kill valve. - A swab valve at the top provides access for well intervention tools like wireline. - Chokes control production rates by restricting flow through interchangeable or

1. Master valves
A valve located on the Christmas tree that controls all flow from the wellbore. A
correctly functioning master valve is so important that two master valves are
fitted to most Christmas trees. The upper master valve is used on a routine basis,
with the lower master valve providing backup or contingency function in the
event that the normal service valve is leaking and needs replacement.
Preeaure gauge
A pressure gauge is used to monitor the pressure of the well. Nowadays, most of
the operators often use electronic gauges so pressure and/or temperature data can
be transmitted via an electronic system for better well monitoring.
Figure 1 master valves
Figure 2 pressure gauge

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Wing Valve:
A wing valve is located on the side of a Christmas tree and it is used to control or
isolate production from the well into surface facilities. Depending on each design
of a Christmas tree, it can be equipped with one or two wing valves. Some
operators require two production wing valves, one as a main production and
another one as a backup (Figure 3). In many cases, one wing valve is used for
production and another wing valve is used as a kill wing valve (Figure 6).
Swab Valve
On a Christmas tree, a swab valve is the topmost valve providing vertical access
to the well for well intervention operations conducted by wireline, slickline,
coiled tubing or a snubbing unit.
Figure 3 Wing
Valve
Figure 4 Production and Kill
Wing Valve
Figure 5 swab valve

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Choke:
Choke is the smallest restriction in a Christmas tree, and its function is to control
the production rate of a well. It is also use to control sand production in some
cases. A choke restricts areas for production flow through a bean or an orifice
inserted into a choke body. The smaller diameter of the beam results in the lower
the production rate. Two types of chokes are 1) positive choke with
interchangeable beans 2) adjustable choke which allows adjusting the choke size
easily.
Figure 3 choke valve

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Reference:
1. Jr. Adam T. Bourgoyne, 1986. Applied Drilling Engineering (Spe
Textbook Series, Vol 2). Edition. Society of Petroleum Engineers.
2. J.J. Azar, 2007. Drilling Engineering. Edition. PennWell Corp.
3. The Australian Drilling, 1997. Drilling: The Manual of Methods,
Applications, and Management. 4 Edition. CRC Press.
4. Steve Devereux, 1999. Drilling Technology in Nontechnical Language.
Edition. Pennwell Pub.