Mechanism and modelling of CO2 corrosion on downhole tools

The conditions surrounding oil and gas exploration are becoming more hazardous, especially in oil and gas fields with a high quantity of corrosive components such as CO2. CO2 causes localised corrosion of tools made from metal, rubber, and other materials in humid environments; this leads to corrosion failure in metal equipment and downhole tools such as drills pipes, casings, and oil pipes, thereby reducing their service life. In this study, the composition, lattice, and crystalline forms of corrosion products and corroded materials were analysed using scanning electron microscopy, energy spectrum analysis, X-ray diffraction, and polarization curves, in order to investigate the corrosion mechanisms and influential factors for several common tool materials. A CO2 corrosion model was established for two materials and the results were verified with optimal prediction values.