American Oil and Gas Reporter - April 2016 - 83

SpecialReport: Drill Bits & BHAs
more rounded shoulder gives us more area
to put cutters, so we have greater redundancy. This improves durability on the
shoulder, which generally is the area that
is most prone to damage, especially when
drilling on a motor at significant RPM.
"With the more durable shoulder, we
have been able to go to a more aggressive
design, dropping a blade and angling to a
bigger cut size while maintaining greater
durability than traditional designs," Kitagawa
adds. "Also, the bit holds the directional
driller's desired azimuth and angle extremely
well, reducing the amount of time spent
sliding rather than rotating. These features
allow us to deliver a much higher ROP."
Dual-Action Cutter
Engineered to combine the shearing
action of a conventional PDC cutter and
the crushing action of a tungsten carbide
insert, the Axe element is the latest cutter
innovation by Smith Bits, a Schlumberger
company. Product Champion Pui Amponpun says positioning Axe elements
across the bit face significantly boosts
ROP in a range of applications and improves steerability in directional wells.
"The combined shearing and crushing
capability of the Axe element cuts rock
more efficiently," Amponpun says. "In
fact, it cuts at least 22 percent deeper to
provide higher instantaneous ROP than a
conventional PDC cutter at the same
weight-on-bit and RPM."
She adds that the Axe element's ridgeshaped geometry provides higher impact
resistance and a diamond layer that is 70
percent thicker than that of a conventional
cutter. This results in improved durability
and dull conditions to maintain maximum
ROP throughout the run, she says.
"With reduced cutting force requirements, the AxeBlade bit reduces overall
torque and reactive torque fluctuation to
improve tool-face control in curve applications, enabling better build rates and
higher overall ROP," Amponpun reports.
She says field tests have shown significant ROP improvement compared with
conventional PDC bits. For example, in
the Anadarko Basin, Unit Petroleum Company employed an AxeBlade bit to improve
ROP and reduce torque while drilling
through interbedded formations of shale,
sand and limestone above the Granite
Wash formation. The operator previously
had drilled the 8¾-inch, 3,570-foot intermediate section of an offset well with a
premium PDC bit, achieving an ROP of
75 ft/hr with minimal cutter wear.

The ridged diamond elements on
this AxeBlade bit from Smith Bits,
a Schlumberger company, increase penetration rates and improve steerability by enhancing
cutting efficiency and minimizing
torque fluctuations.

With an 8¾-inch AxeBlade bit, Amponpun says Unit drilled the intermediate
interval from 5,918 to 9,047 feet in a
single run at an ROP of 96 ft/hr, which
was 27 percent faster than the offset ROP.
The bit generated 20 percent less surface
torque with even better dull condition,
she adds, calculating the overall improved
drilling performance saved the operator
14.75 hours of rig time.
"In the Eagle Ford Shale, an operator
used an AxeBlade bit to drill the curve
and lateral sections through interbedded
shale and limestone formations with unconfined compressive strengths between
6,000 and 15,000 psi," Amponpun reveals.
"Such conditions can present challenges
for tool-face control when sliding through
the transitions. In this case, the objective
was to achieve high instantaneous ROP
and maintain tool-face control while
drilling the interval with a single BHA
that included a high differential pressure
motor."
After drilling an offset well using a
conventional PDC bit, Amponpun says
Smith Bits' engineers analyzed the directional response of a formation transition
in the curve section using the IDEAS design platform to verify that an AxeBlade
bit would maintain the tool-face angle
better through the shale and carbonate
transition than the conventional PDC.
Amponpun reports the AxeBlade bit
drilled 3,586 feet in 35 hours with an
ROP of 103 ft/hr-29 percent faster than
previous wells-and enhanced steerability
by reducing reactive torque. "The bit successfully drilled the curve and lateral
sections, delivered greater tool-face control,
and exhibited better dull condition compared with offset runs," she summarizes.

Tough Cutters
With operators drilling deeper and
longer wells, an unexpected trip during
the curve or lateral can be extremely costly,
observes Atlas Copco Engineering Manager
Kyle Johnson. "Excessive tool-face wear
or sluggish penetration rates often are the
cause of a trip, so we worked with drillers
to develop a more durable bit," he relates.
"The result is the Commander™ PDC
series bits, which feature new Dark Matter™ cutters," Johnson says. "These bits
give drillers improved directional control
and steerability, higher ROP, and greater
cutter durability."
Designing a bit that offers both steerability
and speed presents a dilemma, Johnson
says. "In theory, more blades offer more
stability, and by extension, better ability to
control and steer the bit. However, placing
more cutters in contact with the formation
tends to slow drilling," he clarifies.
The new bits resolve the dilemma
with a unique seven-blade design that
Johnson says uses the cutter layout and
density of a five-blade PDC bit. He adds
that a patented discontinuous blade design
allows the cutter layout on the blades to
deal with abnormal downhole drilling
conditions.
"Traditional straight-bladed bits arrange
PDC cutters as tightly as possible on the
blades. These standard bits can be disrupted easily by various dynamic instabilities that are especially common in directional or lateral drilling," Johnson says.
"Commander bits allow us to strategically
place the cutters on the blades to deal
with these instabilities, while still offering
high ROPs."
Using proprietary software, Johnson
says Atlas Copco modeled how the bits
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American Oil and Gas Reporter - April 2016

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