Oil and gas production handbook An introduction to oil ... - ABB Group

The cycle starts with the plunger falling into the well with its valve open.
Condensed gas and oil can pass though the plunger until it reaches bottom.
There the valve is
closed, now with a
volume of oil,
condensate or water
on top. Gas pressure
starts to accumulate
under the plunger and
after a time pushes
the plunger upwards,
with liquid on top,
which eventually flows
out of the wellhead
discharge.
When the plunger
reaches the wellhead
plunger catcher, the
valve opens and
allows gas to flow
freely for some time
while new liquid
collects at the bottom.
After a preset time, the
catcher releases the
plunger and the cycle repeats.
3.7 Well workover, intervention and stimulation
After operating for some time, a well may become less productive or faulty
due to residue buildup, sand erosion, corrosion or reservoir clogging.
Well workover is the process of performing major maintenance on an oil or
gas well. This might include replacement of the tubing, a cleanup or new
completions, new perforations and various other maintenance works such as
the installation of gas lift mandrels, new packing, etc.
Through-tubing workover operation is work performed with special tools that
do not require the time-consuming full workover procedure involving
replacement or removal of tubing. Well maintenance without killing the well
and performing full workover is time-saving and often called well
intervention. Various operations that are performed by lowering instruments
or tools on a wire into the well are called wireline operations.
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