IMPROVING FRACKING POWER & EFFICIENCY
Field trials demonstrate
e-frac efficiencies
STEPHEN WHITFIELD, ASSOCIATE EDITOR
Last year, NOV conducted an eight-month field trial of its
Ideal electric fracturing (e-frac) technology across several
reservoirs in Texas and New Mexico. The tests, completed
in collaboration with NexTier Oilfield Solutions, focused on
measuring the efficiency gains that can be generated by
using an e-frac system. The tests also aimed to demonstrate
that the Ideal technology can help operators maintain high-
horsepower operations without putting excessive strain on
the frac motor.
“What we wanted to focus on was, how do we harness
the electrical capability in the e-frac system to drive better
fracturing performance, lower NPT and improve efficiency
on location?” said Travis Bolt, Product Development Manager
and Head of R&D for Pressure Pumping Equipment at NOV.
“The cost of fracturing continues to be high. We’re seeing an
increase in complexity around frac operations. We’re all con-
verging on that question of, what’s the next step for fracturing
equipment?” At the 2022 SPE Hydraulic Fracturing Technology
Conference in The Woodlands, Texas, on 3 February, Mr Bolt
discussed both the general efficiencies that can be realized
from an e-frac system, which uses a natural gas reciprocating
engine as its primary power source, as well as more specific
field testing results for the Ideal system.
Control of equipment to improve reliability was a major
focus of the field testing. This primarily involved examining
the turndown ratios of the motors, or the ratio of a motor’s
speed relative to the base speed at which it can be operated
safely at 100% torque without suffering thermal damage. An
e-frac system typically has a 100:1 turndown ratio, meaning
that it can operate safely at 100% torque while running at 1% of
its base speed. As an example, Mr Bolt noted that for an e-frac
system nominally rated to run at 1,800 rev/min, a 100:1 turn-
down ratio means that the engine can operate safely at 100%
torque while running at 18 rev/min.
This ability to generate torque at low motor speeds means
that operators can more easily apply torque in a controlled
Continued on page 35
At the 2022 SPE Hydraulic
Fracturing Technical Con-
ference on 3 February,
NOV’s Travis Bolt discussed
the efficiency gains that
were seen during field trials
conducted last year of the
company’s e-frac system.
34 we have much more visibility to steer these efficiencies even
further.” Electric frac pumps
Later this year, Liberty expects to commercially launch a new
electric pump system featuring a multimotor design. The compa-
ny says the digiFrac system will have twice as much horsepower
per unit than conventional pressure-pumping technologies.
The system’s power frame is flanked on either side by a pod
housing five individual electric motors, each of which can generate
up to 400 hp continuously or 550 hp at peak. This design eliminates
the transmission, drive shaft and pinion found in conventional
diesel frac systems and replaces it with a planetary gear system.
The planetary system utilizes a center gear – known as a sun
gear – that serves as the driver of the system. Three exterior gears
– referred to as planets – rotate around the sun gear. Because
the planet gears are evenly distributed around the sun gear, the
system provides higher torque compared with the standard trans-
mission used in a diesel frac system.
Removing the transmission from digiFrac is an example of
improving efficiency at the margins, said Ron Gusek, President
of Liberty. Shifting gears under load using a standard transmis-
sion introduces stress at potential failure points in a conventional
frac pump, increasing the need for maintenance and decreasing
runtime. “If you’ve ever driven a car with a manual transmission,
shifting gears can be a little clunky. Every time you have to shift
gears, there’s a little shock to the system, and that vibration can
be hard on components,” Mr Gusek said. “When we’re changing
gears on a frac pump, it’s no different. With an electric pump, we
have a smooth system where it’s quite literally turning a dial to
ramp up the speed of the pump.”
With the 10 motors working in unison, each pump will pro-
duce up to 4,000 hp continuously, or 5,500 hp intermittently. This
allows operators to remove up to 50% of their pumping trailers per
application. Combining this level of output with tight packaging, which
is enabled by removing the transmission, provides substantial
power density on the well pad. The result is high horsepower
delivered within a small physical footprint.
“If you look at a traditional frac pump, you would see the
radiator system at the front of the trailer, then a 12-cylinder diesel
engine, then the transmission, and then the pump at the very
back. That entire assembly is around 45 feet long,” Mr Gusek
explained. “If you look at digiFrac, all you have are a pump and
the electric motors attached to the sides of that pump. The foot-
print for that 5,500-horsepower pump takes up a space of 8 by 13
feet.” The footprint to deliver double the horsepower is effectively
halved, he added.
Additionally, with 10 motors operating individually at a lower
horsepower, the digiFrac system is better suited to maintain con-
tinuous high horsepower throughout a run, even in the event of
an equipment failure.
“If you have one large motor running and something happens
to that motor, you’re out an entire piece of equipment,” Mr Gusek
said. “But if we have 10 small motors and something happens to
one motor? No problem. We still have nine more motors. That’s
M A R C H/A P R I L 202 2 • D R I L L I N G C O N T R AC T O R