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or when gas cost is low, gas lift is especially attractive.
Continuous-flow gas lift supplements the produced gas with
additional gas injection to lower the intake pressure to the tubing,
resulting in lower formation pressure as well.
A reliable, adequate supply of good quality high-pressure lift
gas is mandatory. This supply is necessary throughout the
producing life of the well if gas lift is to be maintained effectively.
In many fields, the produced gas declines as water cut increases,
requiring some outside source of gas. The gas-lift pressure
typically is fixed during the initial phase of the facility design.
Ideally, the system should be designed to lift from just above the
producing zone. Wells may produce erratically or not at all when
the lift supply stops or pressure fluctuates radically. Poor gas
quality will impair or even stop production if it contains corrosives
or excessive liquids that can cut valves or fill low spots in delivery
lines. The basic requirement for gas must be met, or gas lift is not
a viable lift method [12].
Continuous-flow gas lift imposes a relatively high
backpressure on the reservoir compared with pumping methods;
therefore, production rates are reduced. Also, power efficiency is
not good compared with some artificial lift methods, and the poor
efficiency significantly increases both initial capital cost for
compression and operating energy costs.
Gas lift has the following advantages.
 Gas lift is the best artificial lift method for handling sand or
solid materials. Many wells produce some sand even if sand
control is installed. The produced sand causes few mechanical
problem in the gas-lift system; whereas, only a little sand plays
havoc with other pumping methods, except the progressive cavity
pump (PCP).
 Deviated or crooked holes can be lifted easily with gas lift.
This is especially important for offshore platform wells that are
usually drilled directionally.
 Gas lift permits the concurrent use of wireline equipment,
and such downhole equipment is easily and economically serviced.
This feature allows for routine repairs through the tubing.

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