Characteristics of scales and their impacts on under‐deposit corrosion in an oil production well

Yan Yang*, Xuan Luo, Yousr E. A. N. Elsayed, Chuanshi Hong, Abhijeet Yadav, Magdalena Rogowska, Rajan Ambat

*Corresponding author for this work

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    This study examined the composition and characteristics of scales formed at different depths in an oil production well, which had developed over years of well operation, workovers, and interventions, by the combined use of optical microscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, transmission electron microscopy, and X‐ray diffraction. The iron‐rich scales consist of several mineral phases, including a dominant portion of akagneite and hibbingite, some barite, silicon dioxide, copper sulfide, and small amounts of iron oxide and calcium carbonate. The scales typically have a layered structure consisting of five to six distinct layers, which impacts steel corrosion processes. The type of corrosion beneath the scale surface was found to be diversified. Pitting morphology corresponding to different stages in the development of scales was observed. The relation between pitting density and the extent of corrosion was analyzed. The effects of environmental factors, including calcium, chlorine, oxygen content, steel microstructure, and multiphase flow, on scale formation and corrosion mechanisms, were discussed. The results provide important insights into the formation of scales and the under‐deposit corrosion processes in the oil production tubes.
    Original languageEnglish
    JournalMaterials and Corrosion
    Volume72
    Issue number6
    Pages (from-to)1051-1064
    ISSN0947-5117
    DOIs
    Publication statusPublished - 2021

    Keywords

    • Amorphous
    • Corrosion assessment
    • Pipelines security
    • Pitting
    • Scale deposit

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