Analysis of corrosion perforation of a gas gathering carbon steel pipeline in a western oilfield in China

In the west of China, corrosion perforation and scaling of pipelines occur frequently in the ground gathering system in oil and gas field, and cause serious safety and environmental problems. In the present work, the corrosion perforation of a carbon steel pipeline with a grade of 20 in a western oil field in China was investigated. Optical metallographic microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction were used to determine the most probable causes of the corrosion perforation. The results showed that the internal corrosion of the studied carbon steel pipe was ascribed to the corrosive CO2 gas and the high content of formation water in the internal transporting medium. The formation of loose and porous iron carbonate layer and the scaling layer with poor adhesion could not protect the carbon steel effectively, so that the high concentration of chloride ions in the formation water caused the initiation of localized corrosion possibly by changing the solubility of iron carbonate, and then the localized corrosion pit propagated and eventually caused the perforation.