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

will fall to zero in the
wellhead if the specific
gravity is 800 kg/m 2 (0.8
times water). By injecting
gas into this oil, the
specific gravity is lowered
and the well will start to
flow. Typically, gas is
injected between the
casing and tubing, and a
release valve on a gas lift
mandrel is inserted into
the tubing above the
packer.
The valve will open at a
set pressure to inject lift
gas into the tubing.
Several mandrels with
valves set at different
pressure ranges can be used to improve lifting and startup. Ill: Schlumberger
oilfield glossary
Gas lift can be controlled for a single well to optimize production, and to
reduce slugging effects where the gas droplets collect to form large bubbles
that can upset production. Gas lift can also be optimized over several wells
to use available gas in the most efficient way.
3.6.4 Plunger lift
The plunger lift is normally used on low pressure gas wells with some
condensate, oil or water, or high GOR wells. In this case, the well flow
conditions can be such that liquid starts to collect downhole and eventually
blocks gas so that the well production stops. In this case, a plunger with an
open/close valve can be inserted in the tubing. A plunger catcher at the top
opens the valve and can hold the plunger, while another mechanism
downhole closes the valve.
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