IMPROVING FRACKING POWER & EFFICIENCY
part of our whole design philosophy: What can we do to maximize
our equipment hours as much as possible with as minimum an
amount of maintenance as possible?”
To improve system durability, the power frame was designed
with an internal geometry that improves its resistance to flex and
wear. Instead of creating a bore that is full of straight lines, Liberty
designed it with curves from top to bottom and front to back
to make the flow laminar and reduce the chance of cavitation.
Cavitation occurs when small, liquid-free bubbles form within
the liquid in low-pressure areas. When the pressure increases, the
bubbles collapse and generate shock waves that gradually wear
out the pump.
The digiFrac system will utilize Rolls Royce’s MTU 2.6-MWe
gas generator sets as its primary power source, effectively creat-
ing a hybrid system. This will allow for emissions reductions
– an estimated 25% in CO2 emissions compared with other off-
grid power sources – due to the gensets’ high thermal efficiency,
which helps reduce fuel usage.
“Rolls-Royce has done a lot of work with us to understand how
much fuel we were going to be consuming and how that would
affect the performance of the engine,” Mr Gusek said. “If we’re going
to deliver an electric frac fleet to a location for our customer, we
have to be confident that we’re going to dramatically reduce the
emissions footprint over the best available technology. Gas turbines
are great at delivering a huge amount of power into a small pack-
age, but the natural gas engine offers that opportunity of delivering
an efficient footprint that is better than the best available.”
Through a comprehensive testing program that included dura-
bility testing and four field trials completed in Q2-Q3 2021, the
system registered approximately 1,500 hours of operation in the
yard and on four pads – two in the Permian Basin and two in the
Denver-Julesburg Basin. While Liberty has not released details
from those field tests, it said results “affirmed confidence for com-
mercial production.”
In its Q3 2021 earnings call, Liberty had announced multi-year
agreements to commercially deploy the digiFrac technology in
2022 with two of its field-trial partners. Then, in the most recent
earnings call on 9 February, the company said it plans to start
deploying digiFrac pump systems into its frac fleets in early Q2
this year. DC
Click here to watch a video interview
with Turner Hall about GD Energy
Products’ Thunder 5000 HP pump.
Continued from page 34
manner, progressively increasing it over a period of time
instead of applying maximum torque all at once, which could
place unnecessary stress on the motor and pump. It also
allows users to increase pressure from the frac pump without
overstressing the system.
The ability to apply torque in a controlled manner, com-
bined with an electric motor’s ability to generate torque values
greater than 100% for short periods of time, can help minimize
the need for manual intervention on downhole issues. To dem-
onstrate this capability with the Ideal system, one of the tests
during the field trials focused on stuck augers. A 12-in. auger
was run on a 45° angle with both the e-frac and a conventional
frac system. Support testing prior to the field test showed that
the motor required between 225% and 275% torque to break the
auger free without manual intervention.
Testers applied torque progressively to the e-frac system,
reaching 260% torque in 3s. As a conventional diesel frac sys-
tem is unable to attain that level of torque, manual intervention
is typically required when the auger becomes stuck.
By providing the ability to address a downhole issue without
stopping operations, “we’ve prevented a person from having
to go out into the field and manually interact with a piece of
equipment,” Mr Bolt said.
Another focus area of the testing was the process of con-
verting raw fuel into energy applied at the wellhead, and its
impact on horsepower and engine efficiency, defined as the
ratio of work performed to the heat provided by an engine.
Electricity is subject to the Joule effect and magnetic losses
as it’s transported within a conventional system. These losses
can account for up to a 2.5% loss in overhead line transmission.
Another loss in the electrical system is the inefficiency of the
step-up and step-down transformer, which typically ranges
from 1% to 2%.
An e-frac system can mitigate the losses typically seen in
a conventional system, primarily because it consumes the
same amount of power as it generates, Mr Bolt said. NOV and
NexTier found that an e-frac system powered by natural gas
internal combustion generators can achieve a 4% increase in
efficiency over conventional systems.
“With mechanical systems, we have to worry about the ini-
tial energy conversion process of diesel fuel into mechanical
energy through a transmission, or through a pump,” Mr Bolt
said. “Typically, you have inefficiency at the generator source.
You lose energy at the transmission due to magnetic losses,
and then you have more inefficiency when you drop down in
torque. But when we looked at the data from our tests, what we
found was that, due to the initial efficiency gains that you have
with natural gas-powered systems, we’re seeing an increase
in efficiency versus a conventional system. In the world of
efficiencies, a 3-4% increase is a big deal.”
NOV and NexTier have said they expect to deploy the Ideal
fleet in the first half of 2022. DC
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