Progress in Research on Ni-Based Protective Coatings for Downhole Tubing Steel in CO2 Flooding

Abstract

Ni-based coating, as an excellent anti-corrosion material, is widely used in the petroleum field and has become a research hotspot in recent years. With the continuous progress of the petrochemical industry, especially in the carbon capture, utilization, and storage and enhanced oil recovery (CCUS-EOR) systems, Ni-based coatings face significant challenges. Based on the latest research status, this paper describes the influence factors of Ni-based coatings and the applicability of different Ni-based coatings. Research shows that CO2 and H2S are the key factors affecting corrosion. With the increase in CO2 and H2S content in the environment, the corrosion rate of carbon steel will be accelerated. When the CO2 content reaches a certain critical value, further increasing the CO2 content will reduce the corrosion rate. The corrosion mechanism of carbon steel under the combined action of CO2 and H2S was also analyzed. At a high CO2/H2S partial pressure ratio, the corrosion process is dominated by CO2 corrosion, and with the increase in the H2S/CO2 partial pressure ratio, the corrosion process shifts to H2S corrosion control. The application of Ni-P protective coatings in this corrosive environment has been investigated. A surface Ni-P coating is extremely hard, wear-resistant, and corrosion-resistant. It can withstand the corrosion of CO2, high salinity, and other media while preventing electrolyte penetration. It exhibits strong corrosion resistance in NaCl solution and can help prevent scaling. However, in the presence of CO2-H2s, it has been discovered that due to inherent faults in Ni-P, the corrosion phenomenon may be exacerbated by the action of H2S, and its protection ability has to be further investigated. The mechanical properties and corrosion resistance of the coating can be enhanced by adding particles to the coating, and four new coating systems, Ni-Fe-P, Ni-Cu-P, Ni-W-P, and Ni-W-P-nSiO2, were introduced. Finally, the future development focus and prospect of CO2 corrosion protection coatings under harsh conditions are prospected.