I N NOVATI N G WH I LE DR I LLI N G
Industry seeks ways
to understand and fight
elusive downhole enemies
Dysfunctions like HFTO can be hard to detect, but companies are identifying
mitigation solutions through sensors, bit studies, predictive software
BY STEPHEN WHITFIELD, ASSOCIATE EDITOR
I n operators’ quest to maximize the value they get from each
well by drilling longer and more complex bores, they’re also
having to deal with a higher risk of encountering downhole
dysfunctions, such as high-frequency torsional oscillation (HFTO)
or lateral shock. Such events can potentially lead to damage in
the BHA and other downhole tools, adding time and cost if they
have to be pulled prematurely. Understanding the nature of these
dysfunctions has, therefore, become more important than ever.

“In the industry, we’re always chasing ROP, trying to get the best
drilling performance we can. But getting the best performance
is not always tied to ROP,” said Raju Gandikota, Co-Founder and
Chief of Innovations at MindMesh, an engineering software and
technology development company. “It’s about managing the tool
Highlights
Testing of various sensors and their
placement showed that HFTO cannot be
detected from the surface.

Bit wear and cutter placement were found
to be among drivers of HFTO vibration
magnitude.

Near-real-time data streams can be
integrated with predictive models in a
digital twin to see how dysfunctions occur
as the drill string moves downhole.

22 life, having vibration control and maintaining the effectiveness of
your tools so that you can actually reach total depth.”
To better anticipate downhole dysfunctions and stave off their
more destructive effects, some companies are testing different
sensor types and various placement to see how they can more
effectively detect HFTO, while others are studying the relationship
between different bit designs and HFTO. Predictive software is
also poised to provide the industry with more information needed
for better decision making to prevent or mitigate downhole dys-
functions. While these approaches differ, the common goal is to
understand the source of damaging vibrations so that downhole
tools can become more durable and stay in the hole longer.

“How many times does a customer come to us and say, hey, we
are losing expensive downhole tools?” asked Prabhakaran Centala,
Engineering Manager for PDC Cutter Technology at NOV. “If they
bring these failures to the table, then we have to figure out the best
way to mitigate that. There are so many intricate details that can
help us bring about a different level of performance altogether.”
Understanding and identifying HFTO
HFTO, which is characterized by torsional oscillations of the
drill string or BHA that fall within the 100-300 Hz frequency, can
be particularly difficult to measure and quantify compared with
other types of vibrations, like stick/slip and bit bounce.

If left undetected, HFTO can lead to downhole tool failures, such
as twist-offs, connection cracks in the BHA, washouts and prema-
ture bit dulling. “Nowadays, rotary steerable tools are much more
sensitive, with moving mechanical parts and electrical compo-
nents. Because of this sensitivity and their complexity in nature,
we’re more susceptible to tool failures because of HFTO,” said
John Rodriguez, Drilling Engineer at Occidental Petroleum (Oxy).

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