Galvanic Corrosion Behavior of N80 Steel and 3Cr13 Steel in CO₂ Flooding Oil Wells

Abstract

N80 steel and 3Cr13 steel used as tubing and hydraulic anchors are inevitably coupled in the CO2 flood oil well, which is prone to galvanic corrosion. Hence, the corrosion rate test and galvanic corrosion test of N80 steel and 3Cr13 steel under CO2 environment were carried out, for clarifying the galvanic corrosion laws of the two steels under the action of various factors including CO2 content, temperature, pressure and salinity. Results showed that the galvanic corrosion occurred at the two steels in CO2 flooding oil wells. 3Cr13 steel was the cathode, which was not affected by galvanic corrosion. In contrast, N80 steel was the anode, and its galvanic corrosion rate increased, which exhibited the same trend as the conventional corrosion, namely increasing with the increase of CO2 content, temperature, pressure and salinity. In addition, the galvanic corrosion sensitivity factor decreased with the increase of CO2 content and pressure. When the CO2 content reached 20%, the galvanic corrosion sensitivity factor was negative, which decreased first and then increased with the increase of temperature, and increased with the increase of salinity. Besides, the maximum galvanic corrosion rate was 69% higher than conventional corrosion rate.

Keywords

• co₂ flooding; n80 steel; 3cr13 steel; galvanic corrosion; corrosion rate; galvanic corrosion sensitivity factor