Analysis of 20 Steel Sewage Pipe Corrosion Failure in a Shale Gas Field

In order to investigate the causes of corrosion-induced perforation failure of 20 steel sewage pipes in a shale gas field，scanning electron microscopy (SEM)， energy dispersive spectroscopy (EDS) and Raman spectroscopy were used to observe the corrosion morphology and characterize the corrosion products of the sewage pipes in a shale gas field.Corrosion simulation tests were conducted based on the actual operating conditions， and the causes of corrosion failure of the 20 steel sewage pipes were systematically analyzed.Results showed that there were sulfate-reducing bacteria (SRB)， saprophytic bacteria (TGB) and other bacteria， and the sewage had a significant scaling tendency.The corrosion products on the sewage pipe surface were mainly Fe2O3， FeCO3， and FeOOH， with Cl and S elements accumulated in the pits under the corrosion layer.As the immersion time in sewage increased， the uniform corrosion rate and the maximum pitting corrosion rate of the 20 steel initially decreased and then increased， with the pitting depth increasing rapidly in the later stage of corrosion.Under-scale corrosion and bacterial corrosion were identified as the main factors contributing to the corrosion failure of the sewage pipes.