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Additionally, dual gas lift is difficult to operate and frequently
results in poor lift efficiency. Emulsions forming in the tubing,
which may be accelerated when gas enters opposing the tubing
flow, also must be resolved.
As the name implies, intermittent flow is the periodic
displacement of liquid from the tubing by the injection of high-
pressure gas. The action is similar to that observed when a bullet is
fired from a gun. The liquid slug that has accumulated in the
tubing represents the bullet. When the trigger is pulled (gas lift
valve opens), high-pressure injection gas enters the chamber
(tubing) and rapidly expands. This action forces the liquid slug
from the tubing in the same way that expanding gas forces the
bullet from the gun. The disadvantage of intermittent-flow gas lift
is the "on/off" need for high-pressure gas, which presents a gas-
handling problem at the surface and causes surging in the flowing
bottomhole pressure that cannot be tolerated in many wells
producing sand. Because of the intermittent production of the well,
intermittent-flow gas lift is not capable of producing at as high a
rate as continuous-flow gas lift. Intermittent flow should not be
considered unless the flowing bottomhole pressure is low, and the
well is gas lifting from the bottom valve.
The intermittent gas-lift method typically is used on wells that
produce low volumes of fluid (approximately < 150 to 200 B/D),
although some systems produce up to 500 B/D. Wells in which
intermittent lift is recommended normally have the characteristics
of high productivity index (PI) and low bottomhole pressure
(BHP) or low PI with high BHP. Intermittent gas lift can be used
to replace continuous gas lift on wells that have depleted to low
rates or used when gas wells have depleted to low rates and are
hindered by liquid loading.
If an adequate, good quality, low-cost gas supply is available
for lifting fluids from a relatively shallow, high gas / oil ratios
(GOR), low PI, or low BHP well with a bad dogleg that produces
some sand, then intermittent gas lift would be an excellent choice.
Intermittent gas lift has many of the same
advantages/disadvantages as continuous-flow gas lift, and the
major factors to be considered are similar. Only the differences are

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