FAILURE ANALYSIS: Volatile Fatty Acid-Enhanced Carbon Dioxide Corrosion of a Multiphase Well Fluid Pipeline

摘要

Failure investigations of the premature rupture of a 12-in. (305-mm) well fluid pipeline were carried out with simulation studies using a high-pressure, high-temperature autoclave. The mechanism of volatile fatty acid-enhanced carbon dioxide (CO_2) corrosion was identified for the first time in an Indian offshore field as a primary cause of the failure. It was found that 350 ppm of volatile fatty acids in the well fluids doubled the CO_2 corrosion. These acids preferentially reacted with protective iron carbonate on bare surfaces to form water-soluble salts. This led to localized acid penetration and severe pitting corrosion, phenomena that eventually led to the pipeline rupture.