Study on the Applicability of Ni-W Coated Tubing in CO₂ Injection Well Environments

For studying the applicability of Ni-W coating in CO2 injection wells， the corrosion behaviors of Ni-W coatings were studied by high temperature and high - pressure corrosion simulation experiments combined with scanning electron microscope (SEM)， laser confocal microscope and X-ray diffractometer (XRD).Results showed that the Ni-W coating had certain uniform corrosion resistance under the condition of supercritical CO2 containing impurities injection condition， but there was localized corrosion risk.In the case of CO2 injection well with formation water reflux， a small amount of H2S would induce severe corrosion failure of Ni-W coatings， resulting in cracking and local damage of the coating.In the case of high oxygenated CO2 injection well with formation water reflux， micro-cracks would be formed in Ni-W coatings，and corrosion products would be generated at the inner and outer coating interfaces.