Research On Corrosion Behavior Of Super 13Cr Oil Casing Steel Under CO₂ Environment In The Complexed Oil Fields

In this paper, high-temperature autoclave and electrochemical testing system were used to study corrosion behavior of super 13 Cr oil casing steel under the stress and the stress state in simulated oilfield CO2 environment. Corrosion morphology and product membrane composition was analysised by using SEM, EDS techniques.The results showed that corrosion rates of super 13 Cr oil casing steel increased at first then decreased with the CO2 partial pressure and H2 S partial pressure increased under CO2 environment. The corrosion rates of super 13 Cr oil casing steel increased with the load stress increased under CO2 environment. Corrosion rates were maximum when CO2 partial pressure was 3MPa,H2 S partial pressure was 0.5MPa,Load stress was 90%. The maximum corrosion rates of super 13 Cr oil casing steel was 0.072 mm/a,it’s result was moderate corrosion, and show a good corrosion resistance of super 13 Cr oil casing steel.The super 13 cr oil casing steel stress corrosion cracking occurs when temperature is 150 ℃, CO2 partial pressure was 4 MPa, H2 S partial pressure was 0.5MPaPitting test results show that increasing of load stress and temperature, the pitting corrosion resistance is decreased. Polarization curves showed that increasing of load stress and temperature, spontaneous corrosion potential negative shift, corrosion intensifies, the pitting corrosion resistance is decreased.