American Oil and Gas Reporter - April 2016 - 86

SpecialReport: Drill Bits & BHAs
erations as we are, so we have similar
backgrounds and philosophies," he suggests. "We both appreciate making a call
and getting to talk with someone who
can make a decision right away.
"As our customers have had to reduce
their costs, we have joined them," he
says. "When a drilling operator tells us
he needs to cut costs by a certain percentage to stay in business, we have done
everything we can to help. Our margins
are much slimmer than they used to be,
but that is what we need to do to make
sure we all stay busy."
Gault points out that many of GT Engineering's Kansas customers continue
to use roller cone bits. "The bits are
slower than PDCs, but they also are
gentler on the rig," he observes. "In shallower wells, that can make up for the
time savings PDC bits provide."
Durable Roller Cone Bit
While PDC bits continue to improve,
roller cone or diamond impregnated and
natural diamond drill bits still have a
place when drilling extremely hard and
abrasive formations, contends John Evans,
product manager for drill bits and services
at Halliburton. With that in mind, he says
the company is preparing to launch a
next-generation roller cone bit, StrikeForce™, that he says will improve both
performance and reliability.
"The seals on the new bit have been
redesigned to enhance bit life and performance," Evans reports. "They feature

a proprietary seal geometry that optimizes
the contact pressure profile on the bearing's
dynamic sealing surface. The highest
contact pressure is at the seal's outside
edges, where protection is most critical
to prevent contaminants from entering
the bearing system. Lower contact pressure
at the seal's center reduces torque and
associated heat generation, extending seal
life more than 50 percent."
The bits' mechanical pressure compensators aim to significantly improve
the durability of the redesigned high-load
capacity bearing and seal system by reducing seal stress, Evans says. These technologies are packaged in a dual-seal/dualcompensator configuration so that the
main reservoir system delivers patented
high-load-capacity grease to the bearing,
and provides pressure management to the
primary seal. Evans points out that patented
intergland grease and pressure compensation between the primary and secondary
seals is provided by an isolated secondary
reservoir, allowing the greases to be optimized independently for improved seal
life and bearing capacity.
"To increase bit life, we also are enhancing the arm geometry to create directed
lifting surface and flow channels that remove cuttings and more efficiently transport
them away from the bit," Evans adds.
"In addition, the nozzles are directed
toward the leading edge of the cutting
structure to increase fluid velocity across
its face, which promotes a sweeping
action across the cutting interface," he

Available in diameters as great as
45 inches, the Everest™ roller
cone family from Varel Oil & Gas
Drill Bits is geared for demanding
applications. Advanced shirttail
protection, refined lubrication
systems and seal-protecting pressure attenuators help the bits stay
on bottom in hard, abrasive formations.

86 THE AMERICAN OIL & GAS REPORTER

A new seal design and a cutting structure
that balances loading among each arm
and cone enable Halliburton's StrikeForce™ bits to offer reliability and speed.

reports. "This fluid path improvement
reduces the amount of cuttings that get
suspended near the bottom of the hole
and reworked, increasing ROP."
StrikeForce bits employ Halliburton's
patented Energy Balanced® cutting structure, which Evans says is balanced to
equalize the bearing loading among each
arm and cone, and to optimize cutter
placement and orientation. "The goal is
to improve ROP, extend bit life, and
reduce vibration," he outlines.
In combination with application-specific
engineering, Evans says StrikeForce has
performed well across the globe. To illustrate, he cites an application in Canada's
Liard Basin, where the rock is extremely
hard and abrasive with strengths ranging
from 25,000 to 40,000 psi. An 8½-inch
StrikeForce bit drilled 610 feet at 16 ft/hr,
which was a record for the area.
Large-Diameter Roller Cone
For large-diameter wells, Varel Oil &
Gas Drill Bits has introduced the Everest™
series of roller cone bits. With diameters
ranging from 14¾ to 45 inches, Varel
says the bits deliver superior performance
and reliability when drilling surface and
intermediate hole sections.
"In designing the bits, our goal was to
combine outstanding efficiency in the
upper hole with enhanced durability in
deeper, tougher carbonate sections," says
Thomas Gallifet, Varel's roller cone engineering manager.

American Oil and Gas Reporter - April 2016

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