Evaluation of Mechanical Properties of Heavy Oil Injection and Production Pipelines in Multi-Component Thermal Fluid Corrosive Environment

Aiming at the problem of dynamic changes in mechanical properties of oil pipes (N80 steel), casings (J55, TP90H, P110 steel) and surface gathering and transportation pipelines (20#) in the multi-component thermal fluid corrosion environment during the thermal recovery of heavy oil. Based on high-temperature and high-pressure corrosion experiments and tensile experiments, this article analyzes the mechanical properties of five types of steels containing corrosion damage. The experimental results show that all five types of steel are severely corroded in this environment, Among them, P110 steel and TP90H steel have the highest corrosion rates, which are 7.83mm/a and 5.78mm/a respectively. Combining the scanning results of SEM, EDS and XRD, it was found that the corrosion products are mainly composed of FeCO3, Fe2O3, Fe3O4 and FeOOH, and these iron oxides formed a double-layer film structure on the steel surface, the outer film is loose and porous, and the inner film is relatively dense. Due to differences in the corrosion products of the inner and outer film layers, there are obvious corrosion pits at the clamp end of the corroded specimens. Tensile tests revealed that the yield strength and tensile strength of steel decrease as corrosion damage increases. 1. INTRODUCTION Heavy oil resources are abundant and have significant reserves, and are currently a hot spot for oil and gas exploration and development, both domestically and internationally(Omoregbe & Hart, 2022; Yao et al., 2023) Multi-component thermal fluid thermal recovery technology is a highly efficient method for the recovery of heavy oil. This is achieved by injecting high-temperature and high-pressure thermal fluids, such as steam, hot water, N2, and CO2, which reduce viscosity and aid in the recovery process. N2 is not easily soluble in water and has good compressibility. It also has a high volume expansion coefficient and a certain lifting effect on the fluid. On the other hand, CO2 gas dissolves and reduces viscosity when in contact with heavy oil, which can improve the extraction effect and reduce the interfacial tension of crude oil, ultimately improving its fluidity (Dong et al., 2015).