Under-deposit corrosion of tubing served for injection and production wells of CO2 flooding

The tubing steel served for the injection and production wells of CO2 flooding was investigated using various characterization methods. The results showed the corrosion failure of the tube was caused by the jointed action of sulfate-reducing bacteria (SRB), CO2 and chloride ions (Cl-) during service. The corrosion product film formed on the tubing steel exhibited a bilayer struc-ture. The outer layer was mainly composed of FeS and FeCO3, which was caused by SRB corrosion and CO2 corrosion respectively, and the inner layer was primarily iron oxide and oxyhydroxide caused by Cl- enrichment and CO2 corrosion. FeCO3 was found in both layers. Accordingly, the synergistic effect of SRB and CO2 resulted in the under-deposit corrosion, and the enrichment of Cl- accelerated the localized corrosion.

Automated summary

Through various characterization methods, this study found that the corrosion failure of tubing steel used for CO2 flooding in injection and production wells was mainly caused by the joint action of SRB, CO2, and Cl-. The corrosion product film on the tubing steel exhibited a bilayer structure with FeS and FeCO3 in the outer layer caused by SRB corrosion and CO2 corrosion, and iron oxide and oxyhydroxide in the inner layer caused by Cl- enrichment and CO2 corrosion. Under-deposit corrosion was a result of the synergistic effect of SRB and CO2, while localized corrosion was accelerated by Cl- enrichment.