American Oil and Gas Reporter - September 2016 - 83

SpecialReport: Tubulars Technology
FIGURE 1
Weight Loss Corrosion of New C72900 versus
Other Copper Alloy in Sour Service

Weight Loss Corrosion Rate (0.001 inch/yr)

1,000

Other Copper Alloy
100

C72900
10

0.1
0

40
60
80
Hydrogen Sulﬁde Partial Pressure (psi)

longevity of manufactured components.
Furthermore, techniques to apply tenacious hard coatings using high-velocity
oxy fuel flame methods often are used
effectively to enhance erosion resistance
of C72900 components in the most extreme flow regimes.
Occasionally, in balanced or slightly
underbalanced drilling operations, production fluids can make their way into
the drilling tool environment. To counter
this eventuality, the enhanced coppernickel-tin alloy has a corrosion rate in
sour service more than two orders of
magnitude less than the typical legacy
copper-based material, providing significant benefits in such situations (Figure
1).
Improved flexibility
While providing improved fracture
toughness and corrosion resistance properties, C72900 material also possesses a
high degree of ductility in an alloy system
that has an elastic modulus that is 50
percent less than steel. This means the
component can bend twice as much without suffering permanent deformation, and
tools can be built that can drill wellbores
with a much sharper radius. This allows
greater flexibility in building the wellbore,
and is a significant benefit in drilling
deep, long-lateral horizontal wells.
The radius that can be deployed, and
drilling from the vertical section to the
horizontal leg, is much sharper than what

100

120

could be achieved in the past. Essentially,
the new alloy means that the horizontal
wellbore can be placed into the pay zone
more quickly than previously was possible.
The new copper-nickel-tin alloy also
has been utilized for high-pressure/hightemperature electrical and electronic connectors for signal and power transmission.
These are small pins and sleeves for con-

necting electronic circuits that maintain
their contact force in the connection, including at high temperatures, where other
materials tend to soften, losing the integrity
of the connection continuity.
In these applications, the new alloy
actually will get stronger and maintain
the contact force even better over time.
The material is unique in that it has better
retention of strength at elevated temperature than any other metal system in this
environment.
The new alloys also can be applied in
thin-walled precision tubing for downhole
instrumentation housings and battery
housings, where it offers high strength,
nonmagnetic properties and very good
stress relaxation properties. As the temperature of the drilling environment increases, it tends to cause metals to lose
their strength and capacity to operate at
high temperatures and pressures. Conversely, the alloys do not lose strength,
even in temperatures higher than 350 degrees Celsius.
Filling The Gap
Several service companies are validating the suitability of the new coppernickel-tin alloy for filling a "performance
gap" for more permanent equipment.
Steel tubulars made with 13 percent
chromium (13-Cr) steel can be used reliably up to 150 degrees C and 1.5 percent
hydrogen sulfide partial pressure, but be-

In response to the ever-increasing demands inherent in today's ﬁeld applications, legacy
C72900 alloy has been re-engineered with next-generation capabilities to give engineers
and designers new capabilities while also providing cost-saving opportunities. The new
tempers provide increased fracture toughness without sacriﬁcing strength.

SEPTEMBER 2016 83

American Oil and Gas Reporter - September 2016

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