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Material Qualification of Sour Service Grades for Extreme Sour Conditions

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Oil and gas operations are pushing the limits of Sour Service always further with the need to combine high Sulfide Stress Cracking resistance (SSC) in H2S partial pressure while keeping high levels for Specified Minimum Yield Strength (SMYS). Operators are indeed entering into new drilling challenges when targeting complex well formations where production casings could be exposed to Sour Service environment and tubing completions to increased differential pressure. Having high levels for Specified Minimum Yield Strength (SMYS) paves the way for addressing Multi-Stage Fracturing (MSF) developments that reach pressure differentials as high as 15,000psi during fracturing operations in challenging environments with minimum intervention possibilities.

Product Number: 51323-19113-SG
Author: John Fortaillier, Florian Thébault, Carine Landier, Nicolas Bouchart
Publication Date: 2023
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$20.00
$20.00

Extreme sour wells presenting H2S partial pressures much higher than 10 bar are frequent in several Middle Eastern areas and such situation are not covered by ANSI NACE MR0175 / ISO 15156 environmental severity diagram. The Sulfide Stress Cracking resistance of OCTG grades is a major concern, especially for high strength material at 110 ksi SMYS. Material qualification program combining NACE TM0177 Method A (Uniaxial Tensile) and NACE TM0316 (Four-Point Bend) was performed to cover risk of Sulfide Stress Cracking (SSC). Additionally, hydrogen electrochemical permeation tests. Most of the tests were performed at 24°C and 15 bar H2S, which is approximately the maximum accessible pressure at that temperature before forming dense H2S phase. Work performed highlights that material qualifications according to ANSI NACE MR0175 / ISO 15156 may be not enough when material is used at much higher H2S partial pressures than 1 bar H2S. Indeed, electrochemical hydrogen permeation tests performed up to 15 bar H2S show the increase of hydrogen content and permeation fluxes with H2S partial pressure, which illustrates that 1 bar H2S does not correspond to a saturation situation for hydrogen uptake inside steels. It is recommended for such qualifications to use Four-Point Bend test method to limit the evolution of the applied stress due to the corrosion rate while allowing an efficient mitigation of this issue by an increase of the specimen thickness.

Extreme sour wells presenting H2S partial pressures much higher than 10 bar are frequent in several Middle Eastern areas and such situation are not covered by ANSI NACE MR0175 / ISO 15156 environmental severity diagram. The Sulfide Stress Cracking resistance of OCTG grades is a major concern, especially for high strength material at 110 ksi SMYS. Material qualification program combining NACE TM0177 Method A (Uniaxial Tensile) and NACE TM0316 (Four-Point Bend) was performed to cover risk of Sulfide Stress Cracking (SSC). Additionally, hydrogen electrochemical permeation tests. Most of the tests were performed at 24°C and 15 bar H2S, which is approximately the maximum accessible pressure at that temperature before forming dense H2S phase. Work performed highlights that material qualifications according to ANSI NACE MR0175 / ISO 15156 may be not enough when material is used at much higher H2S partial pressures than 1 bar H2S. Indeed, electrochemical hydrogen permeation tests performed up to 15 bar H2S show the increase of hydrogen content and permeation fluxes with H2S partial pressure, which illustrates that 1 bar H2S does not correspond to a saturation situation for hydrogen uptake inside steels. It is recommended for such qualifications to use Four-Point Bend test method to limit the evolution of the applied stress due to the corrosion rate while allowing an efficient mitigation of this issue by an increase of the specimen thickness.

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Design Of Sour Service Material: Combining Metallurgical Design, Laboratory And Full Scale Testing Towards A Novel High Strength Sour Service Material

Product Number: 51322-17615-SG
Author: Michel PIETTE, Florian THEBAULT, John FORTAILLIER, Livia-Raquel CUPERTINO-MALHEIROS
Publication Date: 2022
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During the last decades, low alloyed steels with improved resistance to Sulfide Stress Cracking (SSC) have been developed for covering specific applications as heavy wall casings1 or expandable tubings2 or for reaching higher mechanical properties, such as 125 ksi Specified Minimum Yield Strength (SMYS) materials.3-6 For the latter, relevant sour environments for developed grades are mild, meaning that all sour applications cannot be covered while a strong interest exists for O&G operators to use high strength materials when designing wells. Consequently, there is an incentive to push the limits of use of high strength sour service steels by enhancing their resistance to SSC. Several recommendations were already published when designing high strength sour service grades: hardness level shall be limited as much as possible and be preferentially below 22 HRC7, microstructure shall present a minimum required amount of martensite8 which is well known to be ideal for combining high mechanical properties and high resistance to hydrogen. Besides, many authors highlighted some other influencing parameters related to the material or the process.
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New Material Application Limits of Duplex Stainless Steel in Sour Service

Product Number: 51319-12814-SG
Author: Janardhan Saithala
Publication Date: 2019
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Duplex Stainless steel (22Cr) also known as corrosion resistant alloy (CRA) has been extensively used in oil and gas industry for critical applications such as wet gas production flow lines and pipelines. A number of new sour Oil & Gas projects with high salinity (exceeding 200000ppm NaCl) will be developed in the coming years in Petroleum Development Oman (PDO). So far DSS material is qualified upto 10mbar partial pressure of H2S (ppH2S) in 160000ppm chloride levels. The operating conditions of these new projects are outside these current material operating limits of 22Cr DSS. The objective of the study was to enable wider use of 22 Cr DSS grades (lower cost CRA) in highly sour projects in high chloride environments instead of selecting more expensive CRA materials like 25 Cr super duplex alloy 825 or alloy 625. Pitting crevice and stress corrosion cracking tests were conducted on both parent metal and representative welds in high ppH2S and in high chloride environments. The results established the new threshold sour service limits of DSS material which resulted in significant cost savings for various projects. The paper will present the test results and discuss the opportunities for DSS application.
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Case Study On The Downhole Materials Selection And Sour Service Qualification For A High Pressure, High Temperature Gas Field

Product Number: 51321-16554-SG
Author: Roberto Morana/ Lee Smith/ Sai Prasanth Venkateswaran/ Elizabeth Trillo/Luciana Intiso
Publication Date: 2021
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