Summary
Removing API dope from the makeup process of threaded premium connections
during casing and tubing operations not only reduces the risk of contamination
of the local environment but also provides a cleaner and safer working area.
Conversely, the removal of the antigalling property inherent in API dope
greatly increases the risk of galling damage to connections during power-tight
makeup.
This paper describes various tests carried out to evaluate manufacturers’
claims of having successfully improved the galling resistance of premium
connections by electro-depositing a white bronze (45%Cu-55%Sn) alloy onto
couplings manufactured from high-chrome materials. Galling resistance was
measured by subjecting several test coupons plated with copper and various
alloy compositions to a series of tests designed to generate high stresses to
threaded surfaces. The paper also shows through experimentation how the correct
amount of preload was achieved in a premium connection’s gas-tight seal by
applying a thin lubricating layer (also referred to as a protective film) to
both pin and box threads.
Introduction
Government legislation in some oil- and gas-producing regions restricts or
prohibits the use of dopes that contain heavy metals and other toxic materials.
API dope serves extremely well as an antigalling medium, especially for premium
connections manufactured from materials with high chrome content. For dope-free
connections manufactured from 13% chrome alloy, the antigalling balance was
addressed by improving upon current antigalling treatments such as
electrodepositing copper onto premium threaded connections.
Couplings were plated with various alloys to determine the suitability of
each as an antigalling treatment for dope-free connections. When complemented
by a thin lubricating film applied to both pin and box threads, consistent
makeups and long-term storage protection were achieved. A requirement for the
lubricating film was compliance with Norwegian environmental legislationunder
the guidelines of the Harmonized Offshore Chemical Notification Format (HOCNF).
The lubricating film has been listed in a yellow category as having acceptable
environmental properties
Analysis of test data generated by coefficient-of-friction tests showed that
the lubricating properties of the film were similar to those of API dope.
However, further strain gauge data from premium connection make-and-break tests
showed that torque values for connections treated with the lubricating film
required factoring to achieve optimum strain values in the connection seal.
Further galling tests were carried out in the laboratory using test coupons
plated with various alloys, which made possible a comparative analysis.
Before full-scale production, prospective customers requested a series of field
trials to evaluate the effectiveness of the dope-free system. Range 3 joints
coupled with dope-free JFEBEAR premium connections were run into a test well,
pulled, and then rerun.
Two test specimens were placed into a loading rig and tested to the same
load conditions as determined by ISO 13679 connection application level IV (CAL
IV) for doped premium connections.
Alloy Galling Resistance Trials
The objective of the test was to analyze the galling resistance of various
alloy compositions by increasing thread contact pressures during rotation until
galling was achieved. With the exception of a control test sample that was
plated with copper and lubricated with dope, the likelihood of galling was
further increased by rotating the pin in the box without lubrication and
reducing the contact area by machining two threads to the pin coupon. All pin
and box test coupons (Fig. 1) were manufactured from L80 13% Cr
material; the pins were peened, and the boxes were plated with various
alloys.
© 2007. Society of Petroleum Engineers
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History
- Original manuscript received:
15 December 2004
- Revised manuscript received:
21 April 2006
- Manuscript approved:
13 February 2007
- Version of record:
20 June 2007
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