American Oil and Gas Reporter - April 2019 - 79

SpecialReport: Drilling Technology
also completed the test, but the cutters
worked so well that we could not get
them to break."
In fact, where the full-round cutters
spalled at a weight on bit of 20,000
pounds, the ION 3D did not break, even
when weight on bit was increased to
30,000 pounds while drilling through extremely hard quartzite.
The cutters have reduced torque in
both lab tests and in the field, Roberts
comments. "This minimizes the chance
that the motor will stall and enables the
directional driller to hold angle and steer
the well as planned," he says.
In almost every formation type, Roberts
says ION 3D cutters have improved performance. The exception is in soft, easily
sheared shales, and even there, they match
traditional full-round cutters.
"When we first introduced the cutters,
we took a conservative approach, applying
them only in the cone," he recalls. "However, from experimenting, we now know
we can get much better performance by
adapting various configurations, including
using only shaped cutters on the drill bit."
The Next Step
To further increase efficiency in runs
with varying lithologies, Roberts says,
NOV developed the ION 4DX and 4DXC
cutters. The cutters resemble a rectangular
plateau with steep slopes on every side
except the front.
"The slopes create a V in the front
that acts like a plough; it pushes cuttings
aside to focus the bit's energy on virgin
rock," Roberts details. "In the case of the
4DXC, which combines the V plough effect with the ION 3D's chisel point loading, the stress concentration is maximized
in both directions, axial and shear, to
make the cutter more efficient."
The ploughing effect is not the only
way ION 4D improves cuttings evacuation.
"The slopes on the noncutting sides reduce
the contact area between the cutter and
the cuttings it generates," Roberts says.
"This reduces drag and creates a gap between the cutter and the cutting ribbon.
The drilling fluid flows through that gap
and breaks the ribbon into smaller pieces
that are lighter and easier to carry up the
wellbore."
During initial field tests in the MidContinent and Williston Basin, Roberts

says the 4D cutters have shown great
promise. "We are seeing an additional
15 percent increase in ROP above and
beyond the 20 percent improvement provided by the ION 3D," he details.
Pointed Cutter
By carefully selecting and placing
shaped cutters, bit designers can finetune a proven design's interaction with
the rock to improve ROP and durability
in challenging applications, says Daniel
Brietzke, PDC product manager for Varel
Oil & Gas Drill Bits. "To further improve
on the results gained through standard
product development, design changes
may be made to capitalize on the effects
of shaped cutter technology for a given
application," he comments.
Varel's newest shaped cutter, the
FANG™ scribe cutter, has a pointed
geometry that improves drilling efficiency
by pre-fracturing a smaller contact area,
Brietzke describes. These cutters are
used primarily as secondary cutters and
can be placed on either side of the
standard cutting path to create a fracture
and sweep action that removes more
rock per bit rotation.
FANG cutters are particularly helpful
when drilling through rocks that are difficult to mechanically break down. They
improve ROP and bit life by increasing
cutting efficiency and requiring less weight
on bit than traditional secondary cutters
while providing extra shoulder coverage,

Brietzke reports.
"We developed the cutters to increase
footage and ROP in high wear applications
where bits have more potential for performance gains. The cutters have performed well in both planned trip applications as well as ones that drill until the
end of bit life," he says.
Those applications include STACK
play verticals, which go through a mix
of high compressive strength sandstone
and limestone. According to Brietzke,
redesigning an 8¾-inch, six-blade Voyager™ bit to use the FANG cutters improved average footage by 22.9 percent
while still maintaining average ROP.
The cutters also have been used in
the Permian Basin and the Bakken, as
well as in Canada. They have delivered
ROP increases in short planned trip applications around 11 percent, and the
ability to reach total depth through formations that typically have been very
hard on planar cutting structures, Brietzke
relates. "In fact, Varel is setting field
and operator records almost every time
a new bit with FANG cutters goes into
the ground," he says.
"We are finding more and more opportunities to improve performance with
this type of cutting structure," he adds.
"Right now, we are investigating different
FANG shapes, experimenting with their
use as primary cutters, and testing expanded
utilization opportunities with FANG and
other shaped cutter technologies."
❒

This bit from Varel Oil & Gas Drill Bits uses secondary cutters with a pointed geometry
that concentrates energy into a small area in order to prefracture the rock. Varel says
this improves cutting efficiency and therefore ROP and bit life.

APRIL 2019 79

American Oil and Gas Reporter - April 2019

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