Enhancing the CO2-H2S corrosion resistance of oil well cement with a modified epoxy resin

Abstract

The primary function of cement ring is to support and hang the casing, seal formation fluids and prevent interlayer channeling. However, in high-acid oil and gas fields, the cement ring is susceptible to corrosion by acidic media such as CO2 and H2S, which seriously shortens the production life of oil and gas wells and causes substantial economic losses. Therefore, it is very important to study the anti-corrosion performance of cement ring. Given the excellent bonding performance, high mechanical properties, and good corrosion resistance of epoxy resin, in this study, water-based modified epoxy resin was used as the anti-corrosion material to improve the anti-corrosion performance of oil well cement. The corrosion resistance of cement stone with modified epoxy resin was evaluated in acidic media in gas phase and liquid phase under simulated formation environment, and the corrosion resistance mechanism was analyzed. Studies have shown that the corrosion resistance of cement stone added with modified epoxy resin was significantly improved. After 30 days of corrosion in liquid and gas phase acidic medium, the strength loss rates were 9.8 % and 1.2 %, and the corrosion depths were 3.1 mm and 10.6 mm, respectively. Compared with cement stone without modified epoxy resin, the strength loss rates were as high as 32.1 % and 17.6 %, and the corrosion depths were 16.1 mm and 36.6 mm under the same corrosion conditions. SEM analysis shows that modified epoxy resin improves the corrosion resistance of cement stone mainly by filling pores to improve the compactness of cement stone structure and forming three-dimensional network polymer film to isolate acidic medium.