Study of oil country tubular goods casing and liner wear mechanism on corrosion-resistant alloys

Oil country tubular goods (OCTG) casing and liner wear is a critical problem in today's drilling environments. To put in place practical countermeasures, it is important to understand its mechanism. This paper presents tribological and electrochemical experiments by use of various OCTG casing materials and environmental liquids, along with the in-situ observation and analysis of the rubbing interface. The results revealed that corrosion-resistant alloys (CRAs) showed an adhesive wear mechanism with relatively high wear rates, whereas low-alloy steels showed an abrasive or a corrosive wear mechanism with mild wear rates. The wear rate had a clear correlation with corrosiveness, where the wear rate increased as corrosion current densities decreased. In-situ observation exhibited that corrosion products γ-FeOOH or Fe3O4 were generated and simultaneously scraped by sliding in the case of carbon steel, whereas no corrosion products were generated in the case of corrosion-resistant alloys. In conclusion, CRAs tend to have metal-to-metal adhesion (scuffing) with iron-based tool material, resulting in a high wear rate. However, low-alloy-steel casing can avoid adhesion by oxidizing its surface, resulting in a mild wear rate. © 2018 Society of Petroleum Engineers.