Investigation On The Corrosion Of Carbon Steel For Air Injection EOR Process

In this study, the corrosion performances of the three different pipeline steels (N80/J55/P110) were studied to investigate the corrosion of carbon steel in the process of airinjection environment. The corrosion rates of the three metals under differentcircumstances (the oxygen partial pressure, temperature, time, chloride ion concentrationand pH) and the corrosion inhibition efficiency were evaluated by means ofweightlessness method. Moreover, the microscopic analysis methods such as SEM andEDS were also employed to investigate the corrosion morphologies and structural featuresas well as the corrosion mechanisms. The results showed that with the increase of theoxygen partial pressure, the corrosion rates of the three metals firstly increased thendecreased. The corrosion rates of the three metals increased with the increase oftemperature. With the increasing of time, the corrosion rates of the three metals firstlydecreased then reached stable states. With the increase of the chloride ion concentration,the corrosion rates of the three metals all got maximum values at8g/L. The corrosionrates of the three metals showed a trend of decline with the increasing of pH. Thecorrosion inhibition efficiency of the developed corrosion inhibitor was more than99%under the condition of static experiments, while that of three metals was more than90%under the dynamic experimental conditions. The corrosion rates of three metals under thecondition of dynamic were lower than the corrosion rates under the condition of static.The corrosion product of carbon steel mainly consisted of iron oxide when the corrosioninhibitor was not added. After adding corrosion inhibitor, the corrosion product of carbonsteel was a thin layer of dense protective film.In the process of air injection, a certain amount of CO2was produced from theoxidizing reaction between oxygen with the crude oil. The presence of CO2had a certaininfluence to the corrosion of carbon steel in the process of air injection. The influences ofthe CO2partial pressure on the corrosion rates of the three metals were evaluated by themethods of weightlessness and high temperature and pressure electrochemicalexperiments, combined with microscopic analysis methods such as SEM, EDS. Meanwhile, the developed corrosion inhibitor was discussed under the coexistence of CO2and O2. Results showed the corrosion rates of three metals increased significantly whenthere was CO2in the system. The corrosion rates were linearly increased with theincreasing of the CO2partial pressure. The corrosion inhibition efficiency of the developedcorrosion inhibitor was more than98%under the coexistence of CO2and O2. Microscopicanalysis showed that the corrosion products mainly consisted of ferrous carbonate and ironoxide under this condition.