American Oil and Gas Reporter - June 2023 - 82

SpecialReport: Artificial Lift Technology
Multiphase pumping has been around
for more than three decades after its first
introduction to the industry in the early
1990s. The technology has received recognition
for supporting oil and gas production
from assets that previously were difficult,
and sometimes impossible, to produce.
Today, nearly 1,000 pumps are installed
all over the world serving in:
· Topside and deepwater subsea offshore
production;
· Onshore conventional and shale
and tight formations;
· Steam-assisted heavy oil production;
·
Wet gas production; and
· As a service tool for liquid unloading,
flow assurance and starting shut-in
wells and flowlines.
Invaluable Benefits
From limited pump sizes on single
wellheads to large units with more than
1,000 horsepower in parallel operation
to boost production from an entire field,
multiphase pumping provides invaluable
benefits for:
· Boosting and extending production
from low-pressure reservoirs;
· Minimizing topside facilities and
reducing GHG emissions to comply with
more stringent ESG requirements; and
· Extending and accelerating oil and
gas recovery.
Mature reservoirs that successfully
have been produced with gas lift for
many years will sooner or later reach a
point where the wells' back pressure
compromises gas lift efficiency. Limitations
on the available infrastructure and
topside facilities-including flowlines
combined with constant back pressure-
makes it more difficult to flow the wells
even with fully open chokes.
Typically, operators will look for solutions
that involve extended capital and
operating costs. One common way to
lower back pressure is to increase downstream
flowline pipe diameters and/or
install additional flowlines. Another common
solution is to install increased separation
capacity and volume to allow for
lower arrival pressure. However, on offshore
platforms with limited deck space,
achieving these approaches has been
costly, if not totally impossible. Regulatory
issues are other obstacles to overcome in
the offshore environment.
Another option is to increase gas lift
flow and pressure. While compressor upgrades
have been sufficient in some cases,
it is common to change out the existing
compressors to bigger and more powerful
ones. But again, on a mature offshore
shallow-water structure, changing to larger-horsepower
compressors is cost prohibitive
and the net present value is often
not defendable. In some cases, gas lift
gas can be added using an adjacent platform
with excess compression capacity,
but it will require added marine gas lift
lines. For many assets, costs and regulatory
obstacles can make it impossible.
Gas Lift Case Study
Multiphase pumping offers an alternative
to decreasing gas lift efficiency. In
several cases in the Gulf of Mexico,
pumps have been installed topside for
the sole purpose of reducing back pressure
and restoring gas lift service. It is common
to use clean-burning natural gas engines
that tap into production for fuel gas
service. The deck space requirements for
a pump unit is often reasonable, and if
necessary, a cantilever off the deck can
be added to accommodate the pump.
It is worthwhile to examine a case
study example from a shallow-water Gulf
of Mexico platform that was approaching
declining production. The wells were flowing
8 million cubic feet of gas, 4,000
barrels of oil and 4,000 barrels of water a
day. To optimize gas lift, the flowing wellhead
pressure had to be reduced from 680
to 150 psi. The operator had three alternatives
to accomplish this objective, either:
· Installing a new 12-inch liquids
Multiphase pumping offers a compelling alternative solution for aging wells experiencing
decreasing gas lift efficiency. In several Gulf of Mexico applications, twin-screw pumps
have been installed topside to reduce backpressure and restore gas lift effectiveness.
Many of these installations use clean-burning natural gas engines that tap into production
for fuel gas service.
82 THE AMERICAN OIL & GAS REPORTER
flowline, two-phase separator system and
pipeline debottlenecking modifications;
· Upgrading to a larger-horsepower
compressor with a two-phase separator,
surge vessel, pipeline pumps and a glycol
system; or
· Adding a multiphase pump.
Considering older installations' deck
space and deck load restrictions, it is
very important to reduce size and weight
as much as possible. In this case, a cantilever
was added to a restricted platform
deck to support a twin-screw multiphase
pump driven by a natural gas-fired engine.
The compact unit was shipped by truck

American Oil and Gas Reporter - June 2023

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