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Improved Girth Welding On Seamless Linepipe For High H2S Partial Pressure Condition

Picture for Improved Girth Welding On Seamless Linepipe For High H2S Partial Pressure Condition
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NACE MR0175 / ISO 15156 document part 2 provides material requirements for selecting cast irons and low-alloy steels for sour environments.1 Figure 1 is reproduced from this standard and describes different regions of environmental severity for Sulfide Stress Cracking (SSC): service in region 0 being the least susceptible to cracking, even for very sensitive materials, and region 3 being the worst.

Product Number: 51322-17710-SG
Author: Florian Thebault, Antoine Remy, Laurent Faivre, Sébastien Leconte
Publication Date: 2022
Industries: Coatings and Linings , Coatings
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$20.00
$20.00

O&G industry is more and more cautious about the risk of Sulfide Stress Cracking when low alloyed steels are in contact with aqueous environments saturated by high partial pressures of H2S. According to NACE MR0175 / ISO 15156 part 2, material tested in NACE TM0177 Solution A saturated by 1 bar H2S above 80% Actual Yield Strength is qualified for all regions of NACE environmental severity diagram. Basically, this lab test condition is considered severe enough for widening the admissible field exposure conditions up to 10 bar H2S partial pressure. However, recent works highlighted the existence of a threshold partial pressure of H2S below 10 bar for TMCP seam welded pipes. In the present work, similar situation has been observed for girth welds on X65 seamless pipes: acceptable welds based on hardness
data passed at 1 bar H2S NACE Solution A but failed in a fit-for-purpose condition of 6.8 bar H2S. Improved welding procedure has been defined for reaching the appropriate SSC resistance at this H2S partial pressure. It is recommended to evaluate the SSC resistance of girth welds at the field H2S partial pressure when superior to 1 bar.

O&G industry is more and more cautious about the risk of Sulfide Stress Cracking when low alloyed steels are in contact with aqueous environments saturated by high partial pressures of H2S. According to NACE MR0175 / ISO 15156 part 2, material tested in NACE TM0177 Solution A saturated by 1 bar H2S above 80% Actual Yield Strength is qualified for all regions of NACE environmental severity diagram. Basically, this lab test condition is considered severe enough for widening the admissible field exposure conditions up to 10 bar H2S partial pressure. However, recent works highlighted the existence of a threshold partial pressure of H2S below 10 bar for TMCP seam welded pipes. In the present work, similar situation has been observed for girth welds on X65 seamless pipes: acceptable welds based on hardness
data passed at 1 bar H2S NACE Solution A but failed in a fit-for-purpose condition of 6.8 bar H2S. Improved welding procedure has been defined for reaching the appropriate SSC resistance at this H2S partial pressure. It is recommended to evaluate the SSC resistance of girth welds at the field H2S partial pressure when superior to 1 bar.

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Product Number: 51322-17917-SG
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In Upstream, CRAs (Corrosion Resistant Alloys) are widely selected to handle seawater and brines in piping, valves, pumps, heat exchangers, vessels, and seawater injection1-4. Also, disposal of produced water is commonly performed through injection into spent fields. Water from a variety of sources including produced water, seawater and surface/fresh water may also be injected to create pressure drive for existing fields. Usually dissolved oxygen (DO) is not fully controlled when there are multiple sources of injection water and sometimes even possibility of injection of fully oxygenated water exists. For oxygenated seawater, the PREN (Pitting Resistance Equivalent Number = %Cr + 3.3 *(%Mo + 0.5 %W) + 16 %N) shall be >40 and limits are applied to the temperature4. Other applications involve Solid CRA or cladded production pipelines which may get flooded with seawater during installation and precommissioning.
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