American Oil and Gas Reporter - June 2023 - 87

SpecialReport: Artificial Lift Technology
the liner and the tip of the screw profile.
As the flow stream reaches the discharge,
the liquid phase is more defined
as it becomes exposed to the pump back
pressure. The result is a slipstream of
liquid moving in the opposite direction
of the pump flow. The opposite flowing
liquid is controlled by the back pressure
created by the flowlines, separator and
other process equipment downstream of
the multiphase pump.
When the liquid slipstream backfills,
the gas in the next adjacent pumping chamber
will be compressed. The liquid continuously
fills each subsequent chamber and
the gas keeps compressing. At the point of
equilibrium between gas and liquid pressure,
the recombined multiphase mixture will
exit at the pump discharge. The pressure
increase when liquid is pumped is linear,
but with gas, the pressure increase is nonlinear
and the majority of gas compression
takes place shortly before discharge.
Although the twin-screw multiphase
pump is in the family of fixed displacement
pumps, with help of the liquid slip flow,
it performs perfect isothermal/isentropic
gas compression. Contrary to a conventional
compressor, the multiphase twinscrew
pump also provides pumping functions
and can handle 100% liquid at any
time without depending on a scrubber or
blow case.
To always assure the presence of liquids,
a liquid knockout boot downstream
of the pump traps some of the liquid and
circulates it back to the pump inlet with
the help of the discharge pressure. The
liquids also remove compression heat
from the pump, which unlike a compressor,
does not require additional cooling. With
a gas-driven pump, a recycle line is
needed to start the unloaded pump because
of insufficient torque at low engine speed.
Lowering the flowing wellhead pressure
can result in dramatic improvement with
merely a slight reduction of the back
pressure. Figure 1 shows an example
from a gas lift well that produced mostly
gas with some water and condensate.
This well's production profile tended to
reduce the gas lift effect to the point at
which the well was more or less shut in.
When the multiphase pump was turned
on, tubing pressure fell only 40 psi, but
as can be seen in the figure, gas lift was
stabilized and able to produce the well
as intended by reducing back pressure.
Case histories such as this one point
to the opportunities from using multiphase
pumping to reduce back pressure instead
of other alternatives. The multiphase
pump, combined with speed control,
shows the flexibility to instantly adapt to
the actual conditions of a producing well
and optimize production with lower flowing
wellhead pressure. One of the great
features with the twin-screw multiphase
pump is that pressure boosting is independent
of inlet pressure, giving the operator
the best possible tools to produce
aging gas lift wells with low energy. ❒
SVEN
OLSON SR.
Sven Olson Sr. is a senior consultant for Leistritz Advanced Technologies Corp. His 37year
career at Leistritz includes serving as chief executive officer and president. Olson was
involved in testing and introducing multiphase pumping technology to North America, and he
actively participates in applying and promoting the technology in both the onshore and
offshore sectors of the oil and gas industry. He holds a degree in process engineering and an
MBA from the University of Lund in Sweden.
AYAT
ELKENANY
Ayat Elkenany is director of business development at Leistritz Advanced Technologies
Corp. in Allendale, N.J. She has over a decade of expertise in marketing, public relations,
brand and project management, for various industries from political to scientific equipment
and pharmaceuticals. Elkenany holds a B.S. in psychology and biology from WPUNJ.
JUNE 2023 87

American Oil and Gas Reporter - June 2023

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