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Picture for 09427 Electrochemical Methods for Repassivation Potential Measurements
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Picture for Effect of Pre-pits on Localized Corrosion and Sulfide Stress Cracking Resistance of Duplex Stainless Steel UNS S32205 in Upstream Production Environments
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Effect of Pre-pits on Localized Corrosion and Sulfide Stress Cracking Resistance of Duplex Stainless Steel UNS S32205 in Upstream Production Environments

Product Number: 51324-21031-SG
Author: Guru Prasad Sundararajan; V.T. Aruna; Marc E. Wilms; Navashree Surendran
Publication Date: 2024
$40.00
Components in upstream Oil and Gas production such as flowlines, storage vessels or injector pipelines which are made of duplex stainless steel UNS S32205 can undergo localized corrosion such as pitting or crevice corrosion when exposed to oxygen during shutdowns or turn arounds. Such unintended exposure to oxygen is related to poor maintenance or improper preservation and would normally require replacement of equipment. Further use of such pitted components can be considered but requires re-assessment of the pre-corroded material. Open-circuit Potential (OCP) and repassivation potentials (Erp) were measured on UNS S32205 in simulated flowline brines containing 150,000 mg/L Cl- at 110oC with pCO2 of 4.1 bara. The effect of pre-pits on bare and girth welded UNS S32205 was determined by creating artificial pits at OCP under oxygenated brine conditions and then switching the gaseous environment to sweet (CO2) conditions with continuous OCP monitoring. It was found that in oxygen-free CO2 production environments, existing pits did not grow. Sulfide Stress Cracking (SSC) resistance of pre-pitted solution annealed UNS S32205 specimens was determined through Slow Strain Rate Testing (SSRT) and Ripple Load Testing (RLT) at 90oC in concentrated chloride solutions. An electrochemical method was applied to create a single pit on the gauge surface. Comparison of SSRT and RLT results showed that SSRT is too aggressive for determining the pH2S limits. RLT of both pristine and pre-pitted UNS S32205 in concentrated chlorides with up to 0.3 bara pH2S did not show rupture, while selective attack of the ferrite phase was found (pit-depth < 30µm). RLT of notched UNS S32205 specimens were compared to that of pre-pitted specimens. Implications of these results on the limits recommended in ISO15156 / NACE MR0175 are discussed.
	Picture for Localized Corrosion Limit of Use of S13%Cr (UNS S41427) Connector in Converted Injection Treated Seawater Well
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Localized Corrosion Limit of Use of S13%Cr (UNS S41427) Connector in Converted Injection Treated Seawater Well

Product Number: 51324-20714-SG
Author: Nicolas Larché; Marianne Kleive; Charles Leballeur; Eva Malmanger
Publication Date: 2024
$40.00
Many systems can be converted and used for different applications not initially planned. This is the case for production wells, sometimes converted into water injection wells and for which the production tubing material selection is clearly not adapted for prolonged contact with natural seawater. Oxygen removal treatment must be applied but precise control is not obvious and excursions above zero or close-to-zero oxygen can occur. The production tubing material S13%Cr are known to be sensitive to dissolved oxygen excursions in seawater, but data from the literature cannot precisely help in defining the allowed limits of use. Exploring the possibility to convert a production well into a treated seawater injection well then requires a careful assessment of the corrosion resistance limits of the involved alloys. A series of corrosion tests in treated seawater were designed to assess the limits of use of fast connector made of alloy UNS S41427. The corrosion tests were performed both at laboratory scale and on full-scale fast connectors in a treated seawater flow loops simulating service conditions. For all the performed tests, maintaining the dissolved oxygen content (DOC) at 15 ppb and below never led to localized corrosion and has been considered as a safe condition in terms of corrosion risk for alloy S41427 at ambient temperature. It was found that prolonged dissolved oxygen content (DOC) above 30±10 ppb may lead to initial crevice corrosion after only 4 h of exposure. Globally, a very good correlation between the laboratory and the full-scale test results was found. The critical crevice potential for alloy S41427 was significantly affected by the cleaning process of the tested coupons, while the stop of the corrosion was always measured for potentials reached at DOC < 10 ppb. The proposed methodology, involving both laboratory and full-scale tests, allowed to precisely quantify the limits of use of UNS S41427 in treated injection well. It could be used for any other material and applications to help at designing adapted and reliable engineering diagrams for material selections.