Krishnan_subbed.qxp 27/3/09 04:04 Page 72
Alloy K-500 – Past Failures in Downhole Completion Tools
Figure 5: Schematic Showing the Values of H
2
S Partial Pressure and
failure rather than liquid metal embrittlement from mercury. In
pH Where Failures of Alloy K-500 Were Experienced Compared with
addition, failures of Alloy K-500 components were discovered in an
Current Limit in NACE MR0175/IS0 15156-3 and Proposed Ballot
adjacent, mercury-free field with similar environmental characteristics.
6.0
The Alloy K-500 raw material used for the various components
discussed in the failures came from two different sources using
5.5
different melt practices, including a practice that is currently used.
This is contrary to some of the discussion during the Maintenance
5.0
Panel meeting on the ballots that the past failures were linked to a
single source with questionable melt practices. While some of the
pH
4.5
failed components were made from material supplied from the mill
that had possibly undergone residual work after annealing (from
4.0
mill operations such as cold/hot working and/or straightening) that
could affect cracking resistance, other failed components were
3.5
annealed in-house, thus eliminating the theory that residual work
contributed to the failures.
3.0
0.01 0.1 1 10 100 1,000 10,000
H
2
S partial pressure (kPa)
Conclusions from the Investigation
Field failures 2006 ballot 2007 ballot NACE MR0175/ISO 15156-3
Alloy K-500 saw widespread use as a high-strength material for sour
service in oilfields up to the mid-1980s. However, failures of
a temperature limit for the use of this alloy. Alloy K-500 components downhole tools made from Alloy K-500 were observed in sour
experienced failures both when they were coupled to less corrosion- service during that time, causing Halliburton to abandon Alloy K-500
resistant metals and in situations where they were isolated from in favour of other nickel alloys. The renewed interest in this alloy, as
contact with another alloy via elastomers. Thus, it is assumed that evidenced by the ballots proposed by a JIP based on laboratory
coupling is not a requisite for failure. In some cases of coupling, it testing to extend the performance limits of Alloy K-500 in NACE
was discovered that Alloy K-500 experienced corrosion even when
the low-alloy steel was observed to have experienced very little
corrosion. It was also found that while some of the failed Alloy
The corrosion resistance and
K-500 components corroded extensively, others did not. Thus,
widespread availability of Alloy
failures could occur either by hydrogen damage from cathodic
K-500 placed the metal among
charging, such as HE and GHSC, or from active corrosion via
sulphide stress cracking (SSC). These mechanisms support the the first nickel-based alloys to
intergranular fracture morphology observed in the failures.
be used in oil and gas wells.
High hydrogen contents were measured in most of the failures.
Researchers have shown that the ductility of Alloy K-500 was severely MR0175/ISO 15156, led to re-examination of past failures. In light of
reduced by hydrogen absorption and that aged Alloy K-500 suffers a the evidence presented in this article, it can be argued that the
much greater loss in ductility than when in the annealed condition, current limits for Alloy K-500 would need to be further tightened
which would also explain the mostly brittle fracture surfaces noticed in rather than expanded, as suggested by the ballots. It was also shown
the failures.
13
that the Alloy K-500 raw material used in failed components was not
associated with a single source or a single melt practice, which was
Although the wells in environment 3 produced mercury, the lack of suggested by some to be the reason for the failures. These details
mercury found on the failed components and the high hydrogen support the decision made by the authors’ company to discontinue
content measured in those components supports hydrogen damage the use of Alloy K-500 for downhole tools. ■
1. Fraser JP, Treseder RS, Cracking of High Strength Steels in 5. Efird KD, Failure of Monel Ni-Cu-Al Alloy K-500 bolts in 10. NACE MR0175/ISO 15156, Petroleum and Natural Gas
Hydrogen Sulfide Solutions. In: Tuttle RN, Kane RD (eds), Seawater, MP 23, 1985;4:37–40. Industries – Materials for Use in H
2
S-containing Environments
H
2
S Corrosion in Oil and Gas Production: A Compilation of Classic 6. Wolfe LH, Burnette CC, Joosten MW, Hydrogen Embrittlement in Oil and Gas Production – Parts 1, 2 and 3, NACE
Papers, Houston, TX: NACE, 1981;29. of Cathodically Protected Subsea Bolting Alloys, International, Houston, TX, 2003.
2. Bowers CN, McGuire WJ, Stress Corrosion Cracking of Steel CORROSION/93, Houston, TX: NACE, 1993, paper no. 288. 11. Kane RD, Quiroga P, Evaluation of SSC Resistance of “Sweet”
Under Sulfide Conditions. In: Tuttle RN, Kane RD (eds), 7. Erlings JG, de Groot HW, van Roy JFM, Stress Corrosion Materials in H
2
S Environments for Development of Ballot
H
2
S Corrosion in Oil and Gas Production: A Compilation of Classic Cracking and Hydrogen Embrittlement of High-Strength Non- Guidelines in MR0175/ISO 15156, CORROSION/2008,
Papers, Houston, TX: NACE, 1981;48. Magnetic Alloys in Hot Concentrated Brines, CORROSION/86, Houston, TX: NACE, 2008, paper no. 08099.
3. Report of NACE Committee 1-G, Field Experience with Houston, TX: NACE, 1986, paper no. 162. 12. Krishnan K, Rooker J, Chitwood G, Case-History of
Cracking of High Strength Steels in Sour Gas and Oil Wells. 8. Harris JA, Clatworthy EF, Hydrogen Embrittlement of Environmental Cracking Failures with Alloy K-500 for
In: Tuttle RN, Kane RD (eds), H
2
S Corrosion in Oil and Gas INCOLOY Alloy 925, MONEL Alloy K-500, and INCONEL Alloy Downhole Completion Tools, CORROSION/09, Atlanta, GA:
Production: A Compilation of Classic Papers, Houston, TX: 625 by Slow Strain Method, CORROSION/86, Houston, TX: NACE 2009, paper no. 09080.
NACE, 1981;57. NACE, 1986, paper no. 150. 13. Bryant JR, Wallis E, Ductility of Precipitation Hardenable
4. Tuttle RN, Kochera JW, Control of Hydrogen Embrittlement in 9. NACE Standard MR0175-2003, Standard Material Nickel Alloy Following Hydrogen Absorption, CORROSION/88,
Deep Gas Wells. In: Tuttle RN, Kane RD (eds), H
2
S Corrosion in Requirements – Sulfide Stress Cracking Resistant Metallic Houston, TX: NACE, 1988, paper no. 68.
Oil and Gas Production: A Compilation of Classic Papers, Houston, Materials for Oilfield Equipment, NACE International,
TX: NACE, 1981;193. Houston, TX, 2003.
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EXPLORATION & PRODUCTION – VOLUME 7 ISSUE 1
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