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Hydrogen Embrittlement Failure Of Nickel Alloy UNS N07716-140 Tubing Retrievable Safety Valve Component Installed In A Sour Production Gas Well

Picture for Hydrogen Embrittlement Failure Of Nickel Alloy UNS N07716-140 Tubing Retrievable Safety Valve Component Installed In A Sour Production Gas Well
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A 9-5/8 inch (244.8 mm) Tubing Retrievable Safety Valve (TRSV), which is a type of Sub Surface Safety Valve (SSSV) governed by API Specification 14A, was found to have failed when retrieved during workover operations in a gas production well in June 2019. This TRSV was installed in the well in November 2013 and was in production service from 2015 until November 2018 when the well was shut in for maintenance of surface equipment. In March 2019, with the well still shut in for maintenance, a rapid increase in the tubing-casing annulus (TCA) pressure was observed.

Product Number: 51322-17709-SG
Author: Iyad Al-Buraiki, Qasem Alhassan, Karthik Krishnan, Wade Meaders
Publication Date: 2022
Industries: Corrosion Monitoring and Control , Coatings and Linings , Coatings
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A failure in a Precipitation Hardened (PH) Nickel alloy component used as part of a Tubing Retrievable Safety Valve (TRSV) assembly occurred in an offshore gas well. The partial pressures of H2S and CO2 at the TRSV were estimated to be 333 and 534 psia, respectively. The well also produced 0.1 lb/MMSCF of elemental sulfur. The failed component was manufactured using grade UNS N07716 PH Nickel alloy heat treated to 140 ksi (965 MPa) Specified Minimum Yield Strength (SMYS) and 43 HRC max hardness in compliance to NACE MR0175/ISO 15156-3 standard.1 The well was completed and had been in production for approximately five years with no major issues before it was shut-in to service wellhead equipment. A few months after shut-in of the well for service, a rapid increase in the tubing-casing annulus (TCA) pressure was observed which resulted in the need to workover the downhole completion. During workover operations, the TRSV was found to have parted at a major body component of the TRSV assembly, resulting in only the upper portion of the Top Sub being initially retrieved. Fishing operations later successfully retrieved the remainder of the TRSV. Failure analysis of the component indicated brittle fracture due to Hydrogen Embrittlement (HE) as the cause of the failure. The failure initiated at a high stress location in a box thread of the component and propagated through the component’s cross-section resulting in complete separation of the component into two portions. This paper provides the details of the environment conditions, analysis of the failed component, including metallurgical and engineering analysis, and results of HE testing conducted as part of analysis.

A failure in a Precipitation Hardened (PH) Nickel alloy component used as part of a Tubing Retrievable Safety Valve (TRSV) assembly occurred in an offshore gas well. The partial pressures of H2S and CO2 at the TRSV were estimated to be 333 and 534 psia, respectively. The well also produced 0.1 lb/MMSCF of elemental sulfur. The failed component was manufactured using grade UNS N07716 PH Nickel alloy heat treated to 140 ksi (965 MPa) Specified Minimum Yield Strength (SMYS) and 43 HRC max hardness in compliance to NACE MR0175/ISO 15156-3 standard.1 The well was completed and had been in production for approximately five years with no major issues before it was shut-in to service wellhead equipment. A few months after shut-in of the well for service, a rapid increase in the tubing-casing annulus (TCA) pressure was observed which resulted in the need to workover the downhole completion. During workover operations, the TRSV was found to have parted at a major body component of the TRSV assembly, resulting in only the upper portion of the Top Sub being initially retrieved. Fishing operations later successfully retrieved the remainder of the TRSV. Failure analysis of the component indicated brittle fracture due to Hydrogen Embrittlement (HE) as the cause of the failure. The failure initiated at a high stress location in a box thread of the component and propagated through the component’s cross-section resulting in complete separation of the component into two portions. This paper provides the details of the environment conditions, analysis of the failed component, including metallurgical and engineering analysis, and results of HE testing conducted as part of analysis.

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Picture for On the Susceptibility of Precipitation Hardened Nickel Alloys to Hydrogen Assisted Cracking
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On the Susceptibility of Precipitation Hardened Nickel Alloys to Hydrogen Assisted Cracking

Product Number: 51319-12846-SG
Author: Roberto Morana
Publication Date: 2019
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Precipitation Hardened (PH) Nickel alloys have been widely used in the Oil & Gas Industry for decades as these materials offer high strength and outstanding corrosion resistance in aggressive environments. They are commonly used in high-strength components in downhole wellhead subsea and Christmas tree equipment. However high profile failures of equipment have occurred including tubing hangers cross-overs and subsea bolts with alloys such as UNS N07718 UNS N07716 or UNS N07725. In all these cases the mechanism identified was Hydrogen Assisted Cracking (HAC) as the result of the interaction between atomic hydrogen adsorbed by the alloy and its microstructure.PH Nickel alloys are all subject to precipitation of secondary and tertiary phases which if processed improperly (particularly during hot working and heat treatment) may adversely affect the material properties required for the intended application. Despite the number of scientific and technical contributions produced over the last years the interaction between these complex microstructural features and atomic hydrogen is still not understood and is further complicated by variations in testing approaches used to simulate severe hydrogen charging conditions. The present paper provides insights on the HAC failure mechanism for API 6ACRA PH Nickel alloys comparing findings from numerous studies. In addition implications for currently adopted standards and emerging specifications are also presented and discussed.
Picture for Hydrogen Embrittlement of High Strength Precipitation Hardenable Nickel Alloys
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Hydrogen Embrittlement of High Strength Precipitation Hardenable Nickel Alloys

Product Number: 51319-13161-SG
Author: Michael Dodge
Publication Date: 2019
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The high strength and corrosion resistance of nickel-chromium alloys such as Alloy 718 and nickel-iron-chromium alloys such as Alloys 945 and 945X make them particularly good candidates for use in demanding environments in the upstream oil and gas industry. These materials generally perform well where resistance to sulphide stress cracking and chloride stress corrosion cracking is required. However whilst these alloys are considered ‘NACE compliant' environmentally-assisted failures can still occur.It is generally accepted that for hydrogen cracks to initiate there must be a critical combination of stress susceptible microstructure and hydrogen concentration. In this project the effect of microstructure is explored by heat treating Alloy 718 945 and 945X to standard and non-standard conditions. Tensile specimens were slow-strain-rate-tested in air and under CP to explore sensitivity to hydrogen embrittlement. Finally the effect of a severe stress concentration in the form of a sharp notch was used to determine whether there is an enhanced susceptibility to hydrogen embrittlement due to the presence of local stress raisers. The results are compared with tests undertaken by other authors under various hydrogen-charging conditions.
Picture for UNS N07725 NICKEL ALLOY CONNECTION FAILURE
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51312-01095-UNS N07725 NICKEL ALLOY CONNECTION FAILURE

Product Number: 51312-01095-SG
ISBN: 01095 2012 CP
Author: Steve S. Shademan
Publication Date: 2012
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