Oil and gas production handbook - Process Control and ...

number of completions required, and the possibility of deepening the well at
a later time. For example, if it is expected that the well will be deepened at a
later date, then the production casing must be wide enough to allow the
passage of a drill bit later on. It is also instrumental in preventing blowouts,
allowing the formation to be 'sealed'from the top should dangerous pressure
levels be reached.
Once the casing is installed, tubing is inserted inside the casing, from the opening
well at the top, to the formation at the bottom. The hydrocarbons that are extracted
run up this tubing to the surface. The production casing is typically 5 to 28 cm (2 -11
in) with most production wells being 6 in or more. Production depends on reservoir,
bore, pressure etc. and could be less than 100 barrels a day to several thousand
barrels per day. (5000 bpd is about 555 liters/minute). A packer is used between
casing and tubing at the bottom of the well.
3.4.2 Completion
Well completion commonly refers to the process of finishing a well so that it is ready
to produce oil or natural gas. In essence, completion consists of deciding on the
characteristics of the intake portion of the well in the targeted hydrocarbon
formation. There are a number of types of completions, including:
• Open hole completions are the most basic type and are only used in very
competent formations, which are unlikely to cave in. An open hole
completion consists of simply running the casing directly down into the
formation, leaving the end of the piping open, without any other protective
filter.
• Conventional perforated completions consist of production casing being run
through the formation. The sides of this casing are perforated, with tiny
holes along the sides facing the formation, which allows for the flow of
hydrocarbons into the well hole, but still provides a suitable amount of
support and protection for the well hole. In the past, 'bullet perforators'were
used. These were essentially small guns lowered into the well that sent off
small bullets to penetrate the casing and cement. Today, 'jet perforating'is
preferred. This consists of small, electrically ignited charges that are
lowered into the well. When ignited, these charges poke tiny holes through
to the formation, in the same manner as bullet perforating.
• Sand exclusion completions are designed for production in an area that
contains a large amount of loose sand. These completions are designed to
allow for the flow of natural gas and oil into the well, but at the same time
prevent sand from entering the well. The most common method of keeping
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