A gathering pipeline of an oil field was damaged by a third party at a distance of 10km from the oil transfer station. During the pipe replacement and repair process, operational personnel found symmetrical corrosion grooves at the bottom of the pipeline. The corrosion mode was analysed by chemical composition, microstructure, XRD, scanning electron microscope, and other methods. The results showed that the chemical composition and metallographic structure of the gathering pipeline met the requirements of the standard, and no abnormality was found after a long year of service. Because the heavy oil mixed scale is deposited on the bottom of the pipeline, under the low flow rates of the medium and localized corrosion occurred at the interface between the sludge and the medium, corrosion grooves were formed. It is recommended to carry out regular pigging operations to remove the sludge.
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