I N NOVATI N G WH I LE DR I LLI N G
NOV is working on enhancements of its Delta pipe connection, as well as the development of two newer connections. Addi-
tionally, the company recently finalized the qualification of a 20,000-psi connector on a sour service-grade.
Engineer at TSC Drill Pipe, a division of Texas Steel Conversion.
“I’ve seen a significant increase in slim-hole drilling, which is
when you have a smaller annulus between the drilling tool and
the wellbore,” he explained. “We’re also seeing much deeper wells,
with wellbores averaging a minimum total depth (TD) of 20,000 ft,
and some going to 30,000 ft. This is quite a change from where we
were just a decade ago.”
Drilling contractors, in particular, have called for higher perfor-
mance in the threaded connections that hold the string together
so they can reach those deeper TDs. While there is still some
limited use of single-shoulder API connections, Mr Garrett noted
that most drilling programs now use double-shoulder design con-
nections, with a growing percentage of those being proprietary
thread technology from various providers.
“With double-shoulder connections, we can achieve the higher
makeup torque necessary in these more challenging wells,” he
said. “Additionally, the proprietary double-shoulder connections
typically have a larger bore through the threaded connection,
which improves hydraulic performance in the drilling program.”
On the heels of drilling projects that are incorporating increas-
ingly advanced BHA technology, like automated rotary steerable
systems (RSS) for precise directional control, Mr Garret remarked
that proprietary connections have gained significant market
share, becoming the new standard to enable newer systems to
perform. “If you’re using an API rotary-shouldered connection
for your drillstring threaded connection, it typically has a 2-in.
taper-per-foot thread form, which results in a smaller diameter in
the threaded connection when compared with the manufacturer’s
proprietary connections,” he explained. “Most of these proprietary
connections have a much slower, more gradual taper on the
connection, which is how you achieve the larger inner diameter
necessary to improve hydraulic performance.”
TSC Drill Pipe’s PTECH+ is the company’s most recent entrant
into the high-performing connection market. The connection was
designed to encapsulate the essential characteristics required
for extended-lateral oil and gas drilling: maximized hydraulic
24 performance, increased makeup torque and improved fatigue
resistance. “How do you achieve fatigue resistance on these high-per-
forming connections?” Mr Garrett asked. “When designing
PTECH+, testing and analysis proved that a large radius at the
root of the thread form reduced peak stresses in the connection.
This reduction in connection peak stress mitigates the potential
for connection fatigue and failure when exposed to downhole
bending.” Mr Garret also noted that the materials used to manufacture
the connection impact performance. “There’s been a step-change
in the materials we use, such as steel with a higher alloying
content to provide improved toughness with a higher hardness,”
Mr Garrett explained. “Typically, in steel technology, the higher
the hardness, the more brittle the steel may become. Using better
alloying, coupled with precisely controlled heat treatment, we
can effectively eliminate this problem. This practice increases
the performance capabilities and assures the durability of the
PTECH+ connection.”
Although the connection maintains a streamlined geometric
design, torque capacities for the connection average 85% to 280%
greater than API drill pipe connections of the same dimensions,
according to the company. TSC Drill Pipe recognized that a draw-
back to most higher-torque connections is that they typically
require more turns to make up to be shouldered, compared with
API drill pipe connections. Accordingly, a critical design criterion
was to reduce the number of necessary turns to make up without
sacrificing performance. Depending on the connection size, the
turns to make up range from 7.5 to 9.6.
Another trend with present-day drilling programs and deeper
wellbores is the use of drillstring oscillating programs, which
involve alternating clockwise and counterclockwise rotation of
the drillstring while drilling. “One problem we are seeing result-
ing from these oscillating programs is that the connections may
have a tendency to break out,” Mr Garrett said. “The PTECH+ con-
nection is designed to provide for higher makeup torques on the
M A R C H/A P R I L 2023 • D R I L L I N G C O N T R AC T O R