GEOTHERMAL DRILLING
New ‘walking’ tool anchors the
bit to the rock, aims to mitigate
stick/slip by preventing buildup
of reactive torque downhole
Technology is being developed primarily
with geothermal drilling in mind; prototype
was recently tested on Nabors land rig
BY STEPHEN WHITFIELD, ASSOCIATE EDITOR
Geothermal energy is an increasingly pop-
ular entry point into the renewable space
for drilling contractors, as it can be
accessed using conventional drilling rigs
and equipment. However, deploying geo-
thermal drilling at scale remains a chal-
lenge because, in much of the world, the
high-temperature rocks needed to produce
geothermal energy are located too deep
beneath the Earth’s surface for conven-
tional drill bits to reach effectively.

GA Drilling – which attracted $8 million
in investment from Nabors Industries last
year – has been working on a new tool to
help drillers make deeper holes in hard
formations with greater efficiency. The
Anchorbit walking system aims to miti-
gate stick/slip, which is a common factor
hindering effective drilling in geothermal
formations .

“All the things we’re working on are
aimed at the goal of drilling deeper into
hotter rocks, where the higher energy is
and which is typically igneous and met-
amorphic rocks,” said Brad Ivie, VP of
Engineering at GA Drilling.

The Anchorbit system consists of two
sets of extendable pistons installed above
the mud motor that are designed to grip
the formation as the bit moves downhole.

Speaking at a demonstration of the Anchorbit tool, held at a Nabors facility in
Houston on 25 April, Igor Kocis, CEO of GA Drilling, touted the tool’s ability to miti-
gate stick/slip and, therefore, increase geothermal drilling efficiency.

36 Weight on bit is provided conventionally
from the drillstring, and the pistons act in
concert during drilling: While the lower
set of pistons grips the wellbore wall, the
upper set moves downhole. At the end of
a stroke, the upper pistons extend and the
lower pistons retract, essentially “walking”
downhole. By effectively anchoring the bit to the
rock, the tool absorbs the reactive torque
generated by the bit and prevents it from
building up in the drillstring – stick/slip
occurs when that reactive torque releases,
causing the drillstring to unwind and the
bit RPM to speed up.

The tool also keeps drillers from having
to decrease the weight on bit, a common
method to mitigate stick/slip, Mr Ivie said.

“If we’re going to drill in these hard rocks,
we need to put more weight on the bit
so you can take a bigger depth of cut. If
you spin it too fast, in a lot of these rocks,
you’re going to wear the bit quickly. But
the problem with putting a lot of weight
on the bit is the torsional vibration. When
you’re going laterally into the rock, you
lose a lot of energy, and the drill pipe can
get very flexible. It’s very inefficient to drill
that way.”
GA Drilling held a public demonstration
of the tool, which has been in development
for the past two years, on a land rig at a
Nabors’ testing facility in Houston, Texas,
on 25 April. The demonstration kicked
off a week of proof-of-concept testing of a
prototype, showing that the pistons could
grip into the wellbore wall and prevent the
transmission of force from the bit up the
drillstring during the drilling of a test well.

The testing also demonstrated the walk-
ing capability of the tool, as the pistons
transitioned between gripping the forma-
tion and moving downhole.

“This is our first chance to show
Anchorbit as a viable product that we can
bring to market, where we can show full
integration with the rig,” said Igor Kocis,
CEO of GA Drilling. “We also wanted to test
the basic functionality and the limits of
the tool to give us information and param-
eters that we can use to update the design .”
The current prototype can operate
in a maximum ambient temperature of
300°F, the minimum temperature of rock
required to generate geothermal power,
according to the US Energy Information
J U LY/AU G U ST 2023 • D R I L L I N G C O N T R AC T O R