Corrosion Behaviors of N80 and 1Cr Tubing Steels in CO2 Containing Downhole Environment-A Case Study of Underground Gas Storage in LiaoHe Oil Field

In order to evaluate the effect of chromium content in carbon steel on the corrosion resistance of carbon steel materials, the corrosion behavior of 1Cr and N80 steels was investigated in this study by immersion weight loss method under three different CO2 partial pressure and temperature conditions in formation water for 72, 168 and 336 h. Detailed material surface morphological characterization was performed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and confocal laser scanning microscopy (CLSM). The results show that the pitting corrosion of N80 carbon steel is serious at medium temperature and low CO2 partial pressure (50 degrees C, 0.30 MPa), and the corrosion rate is significantly higher than that of 1Cr steel. However, at high-temperature and high CO2 partial pressure (100 degrees C/0.63 MPa and 114 degrees C/0.73 MPa), 1Cr steel is more inclined to the mesa corrosion dominated by local corrosion characteristics, and the corrosion rate is seriously higher than that of N80 steel with uniform corrosion. From the experimental results, we can know the corrosion resistance of carbon steel and 1Cr steel is not only affected by the corrosion environment, but also depends on the formation process of the product film, as well as its compactness and integrity characteristics. At low-temperature and low CO2 partial pressure, 1 wt.% chromium content can provide a certain degree of corrosion resistance, while high temperature and high partial pressure can broaden the application window of carbon steel N80 and weaken the corrosion inhibition effect of chromium.

Automated summary

The effect of chromium content on the corrosion resistance of carbon steel was evaluated by investigating the corrosion behavior of 1Cr and N80 steels under different CO2 partial pressure and temperature conditions. The results showed that N80 carbon steel exhibited serious pitting corrosion at medium temperature and low CO2 partial pressure, while 1Cr steel showed mesa corrosion dominated by local corrosion characteristics at high temperature and high CO2 partial pressure. The corrosion resistance of carbon steel and 1Cr steel was influenced by the corrosion environment and the formation process, compactness, and integrity characteristics of the product film.