Investigation on the Effect of Temperature and CO₂ Partial Pressure on Corrosion of N80 Tubing Steel in Formation Water Environment

In the process of oil and gas extraction, N80 steel is used as a common tubing material. CO 2 corrosion has become one of the most dangerous problems in its entire life cycle. In this paper, the conditions of different temperatures (90-220 °C) and CO 2 partial pressure (0.2-3 MPa) were selected, and the dynamic rotating high-temperature autoclave was used to simulate N80 steel corrosion in formation water environments. The results showed that the corrosion rate of N80 steel gradually decreased with the increase of temperature, and the corrosion rate was the lowest at 150 °C. In addition to this, with the increase of CO 2 partial pressure, the corrosion rate first increased and then decreased. The corrosion rate was the highest when the CO 2 partial pressure was 0.8 MPa. Through surface analysis techniques (SEM and XRD) and electrochemical tests, it was found that the corrosion resistance of N80 under high temperature and high pressure is closely related to the corrosion product film (FeCO 3 ). The compactness of FeCO 3 product film determines the corrosion characteristics of the matrix.