Performance Evaluation and Corrosion Perforation Failure Analysis of L80-1Cr Tubing in a Deep Coalbed Methane Well

To investigate the extreme localized perforation of L80-1Cr tubing after only 37 days in a deep coalbed methane well, a comprehensive failure analysis was conducted using physicochemical testing, microstructural characterization, and simulated tests. The results show that the tubing met standard specifications, suggesting that intrinsic material defects were unlikely to be the direct cause. The rapid perforation was likely associated with a synergistic mechanical–electrochemical coupling. Specifically, possible mechanical scraping during wellbore operations may have breached the initial product film, triggering a severe “large cathode–small anode” galvanic effect. Under harsh conditions (60 °C, high CO2 and Cl−), the alloy failed to repassivate. Furthermore, penetrative Cl− was enriched within the scraped pits, while Fe2+ hydrolysis promoted local acidification, initiating an autocatalytic pitting cycle inside the occluded cell that caused rapid external-to-internal perforation. We recommend strictly standardizing operations to avoid mechanical damage, applying targeted inhibitors, and upgrading to 3Cr or higher-grade alloys in high-risk sections.