Abstract
Flue gas injection for heavy oil recovery has received a great deal of attention, because it is more cost effective than lots of other injection methods. However, the corrosion could occur easily, because the flue gas usually contains corrosive gases such as CO₂, H₂S, and O₂. In this work, the corrosion behaviors of G20 steel in flue gas injection environment simulating Xinjiang oil field (China) were investigated using weight loss measurement and surface characterization techniques. The effect of environments including the O₂-containing environment, the H₂S-containing environment, and the O₂-H₂S-coexisting environment on the corrosion of G20 steel in gas phase and liquid phase was discussed. The results show that the corrosion rate of G20 steel in the O₂-H₂S-coexisting environment is much higher than the sum of corrosion rates of the O₂-containing environment and the H₂S-containing environment, regardless of the gas phase and the liquid phase. This indicates that there is a coupling effect between O₂ and H₂S, which can further accelerate the corrosion of steel in O₂-H₂S-coexisting environment. The results of surface characterization demonstrate that in a typical flue gas injection environment, the corrosion products are composed of FeCO₃, FeS, FeO(OH), and elemental sulfur. Elemental sulfur could obviously accelerate the corrosion of steel. Therefore, it can be considered that the coupling effect of O₂ and H₂S on corrosion of G20 steel in flue gas injection environment is caused by the formation of elemental sulfur in corrosion products.