Recently, there are dozens of corrosion perforation failures of API 5CT Grade L80 (3-1/2") tubing within 2 years in water injection wells in a middle east oilfield, where the dissolved oxygen in injection water is about 0.05 mg/L and the temperature is no higher than 333 K (140 °F). In this paper, optical metallographic microscopy, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD), combined with the weight loss and bacteria test bottles are used to find out the reason of corrosion perforation in such a short time. The results indicate that the material properties of the failure L80 tubing meet the API SPEC 5CT-2011 standard requirements and the corrosion rate of L80 in simulated injection water is 0.054 mm/a at 333 K (140 °F). The bacteria both in injected water and corrosion product are detected. In addition, the corrosion product of the failure tubing is mainly FeS, CaCO3 and Fe3O4, which indicates that microbiologically influenced corrosion contributed to the observed corrosion.

Subject
X-ray diffraction, Corrosion failures, Water, Perforation, Metallography, Corrosion products, Tubing, Mechanical failure, Corrosion morphology, Bacteria, Water injection, Dissolved oxygen, Microbiologically influenced corrosion
Keywords:
Microbiologically Influenced Corrosion, Corrosion Perforation, Failure Analysis, Water Injection Well
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2020
Association for Materials Protection and Performance (AMPP)
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