Corrosion Behaviors of 25CrMnVA Steel in CO_2 Flooding Enhanced Oil Recovery System

摘要

Influences of temperature and CO_2 partial pressure on CO_2 corrosion behaviors of 25CrMnVA steel were investigated in the simulated oil field environments. The corrosion rates were measured under high temperature and high pressure condition. SEM, EDS and XRD were used to analyze the morphologies and characteristics of corrosion scales on the steels. The results shows that the corrosion rates of 25CrMnVA steel change little below 65°C, the corrosion feature is uniform corrosion. The corrosion rates increase rapidly after 65°C, mesa corrosion is found on the surface of steel. The corrosion rates decrease firstly and increase subsequently with the rising of CO_2 partial pressure, and the minimal corrosion rate presents near CO_2 critical pressure. The compactness of corrosion scale improves with the increase of CO_2 partial pressure below 8MPa, which causes uniform corrosion rate reduced. Under supercritical CO_2 condition, the local defects in the surface of corrosion scale increase, and the compactness of corrosion scale reduces, which cause the increase of corrosion rate sharply. The corrosion rate and corrosion morphology are closely related to the state of corrosion scale.