Applicability of 3Cr-N80 Steel and N80 Steel in Oilfield CO_2 Environment

摘要

The corrosion performance of 3Cr-N80 and N80 steels in simulated oil field formation water with CO_2 partial pressure of 0.23 MPa at 80℃ was investigated using weight loss measurement and surface characterization techniques. The results showed that 3Cr-N80 steel exhibited better localized corrosion resistance, while N80 steel experienced severe pitting attack under the testing conditions. The corrosion rate of 3Cr-N80 steel decreased sharply at early stage of exposure, followed by decreasing with time, and finally reached a relatively stable value. The formation of corrosion products on 3Cr-N80 steel was rich in Cr content and Cr content was about 8 times higher than that of in the substrate, resulting in high corrosion resistance and providing better protection to the steel. FeCO_3 and Cr(OH)_3 co-deposited films have a critical effect on the CO_2 corrosion resistance of 3Cr-N80 steel. Corrosion products formed on N80 steel surface was composed of Ca(Mg,Fe)(CO_3)_2 where Fe~(2+) was replaced by Ca~(2+) and Mg~(2+) ions.