Major corrosion influence factors analysis in the production well of CO2 flooding and the optimization of relative anti-corrosion measures

Abstract

Major corrosion influence factors in the production well of CO2 flooding in Xinjiang oilfield were investigated, and corresponding anticorrosion measures (relating to corrosion inhibitors and corrosion-resistant alloys) had been contrasted in order to select a most suitable scheme to solve the tubing corrosion issue. The results showed that the corrosion of N80 steel in liquid phase was mainly affected by temperature, while in gas phase by temperature and CO2 partial pressure. As to the corrosion of 3Cr steel, in liquid phase, the influencing factors were temperature and chloride concentration, and in gas phase, it was mainly affected by temperature. The safe service life of N80 and P110 steel in liquid phase were less than 8 years, whereas that of 9Cr and 13Cr steel both exceeded 30 years. In gas phase, the safe service life of N80 and P110 steel were 11.65 years and 16.55 years respectively, while that of 3Cr, 9Cr and 13Cr steel were more than 30 years. Suitable for production well in CO2 flooding, No.6 corrosion inhibitor was selected. The corrosion rate of tubing could be controlled within 0.076 mm/y by adding 1000 ppm corrosion inhibitor. 9Cr steel was recommended to be used as the tubing of new production wells for CO2 flooding, and, for old wells, the method of continuous filling corrosion inhibitor was recommended to resist corrosion.