Study on CO₂ and Microbial Corrosion Behavior of J55 Casing Steel

The corrosion behavior and mechanism of J55 casing steel were studied through uniform and local corrosion tests in simulated downhole environment and electrochemical test analysis.The results show that the CO₂ uniform corrosion rate of J55 casing steel increases gradually with the increase of temperature.When the temperature reaches 60 ℃, the corrosion rate reaches the maximum value of 1.0175 mm/a, and the local corrosion is the most serious.SRB and TGB significantly increase the uniform corrosion rate and local corrosion degree of J55 casing steel.In CO₂ corrosion environment, both the cathode and anode of J55 casing steel show activation reaction, and the corrosion current density under self-corrosion potential is controlled by the cathodic reaction process.When the temperature reaches 60 ℃, the dynamic resistance of J55 casing steel reaches the minimum value and the self-corrosion current density reaches the maximum value.SRB and TGB significantly reduce the self-corrosion potential of J55 steel in CO₂ corrosion environment, while can promote the cathodic hydrogen depolarization process of CO₂ corrosion, so the anodic dissolution of J55 steel is accelerated.