American Oil and Gas Reporter - January 2017 - 87

the well using gas lift.
Paulo Waltrich, assistant professor in
the Craft & Hawkins Department of Petroleum Engineering at Louisiana State
University, says Royal Dutch Shell funded
work with LSU researchers to advance
developing liquid-assisted gas-lift (LAGL)
technology. The LAGL concept uses a
gas/liquid mixture to increase the density
of the injected fluid above that of the
single-phase gas to allow lower injection
pressures for the same bottom-hole pressure requirements, Waltrich says.
He points out the lower injection
kickoff pressure minimizes compression
costs associated with gas-lift systems and
increases gas-lift technology reliability
by decreasing the number of unloading
valves, and thus potential leak points.
"The standard in the industry is to
inject pure, single-phase gas to do this unloading. What Shell was proposing and
started investigating at LSU is injecting a
mixture of liquid-say, water or oil-with
natural gas. That decreases the power required for the compressors injecting the
gas and liquids into the well," he outlines.
A major advantage of LAGL is that it
can be deployed in operating gas-lift systems without significant modification or
costs, he adds. The major modification is
adding a liquid injection system that connects to the single-phase gas lines. "The
system probably will add some intangible
costs, but nothing significant," Waltrich
says. "When you are decreasing the injection pressure that much, the footprint
and the horsepower of the compressors
required will be reduced significantly."
When the system was tested at LSU's
test well, the compression required was
reduced 75 percent in the best case, he
says, pointing out that by adding liquids
to the injected gas, a well injecting at
1,300 psi would need a compressor capable
of 400 psi.
"One of the big advantages of gas lift
is if you have highly deviated wells, a
gas lift is pretty much just injecting fluids.
So, it really does not matter if a well is
horizontal or vertical. This applies to
both," he says. "Also, there are no restrictions with horizontal wells that are
very long."
LSU researchers also are focusing on
how bottom-hole valves that have been
subjected to injected gas only may be
impacted by handling a liquids/gas mixture
for long periods, Waltrich says. "When
you are doing the standard gas lift practice,
you have some sort of liquid in the well
anyway, so this valve already handles
liquid and gas. We have not seen erosion
problems by adding liquid to the valve,"
he reports.
The university is looking for operators

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