Material Selection and Corrosion Evaluation of Three Corrosion-resistant Sucker Rods under CO₂ Flooding Condition

High-temperature and high-pressure dynamic cyclic corrosion test was used to study the corrosion behavior of three types (KH-type, polyethylene-coated type and tungsten-plated type) of anti-corrosion sucker rod materials in flooding well environment at 60℃, containing 20%~80% CO₂, and 19 MPa. Mechanical properties of the three sucker rods were evaluated using an electronic universal testing machine. The results show that in the test environment, KH sucker rod was corroded severely and its minimum corrosion rate was also higher than that of the industry standard, tungsten-plated sucker rod was slightly corroded by CO₂, and polyethylene-coated sucker rod had no mass loss after corrosion and it could be regarded as no corrosion. The corrosion rate of the three sucker rod materials in the CO₂ corrosive environment from small to large was as follows:polyethylene-coated type < tungsten-plated type < KH type. After the three sucker rods were immersed in crude oil containing CO₂, the mechanical properties of KH sucker rod dropped significantly compared with those without immersion. The decrease in mechanical strength of the polyethylene-coated sucker rod was small. The mechanical properties of tungsten-plated sucker rod samples were the best. It is recommended to use tungsten-plated sucker rod as an anti-corrosion sucker rod for CO₂ flooding wells.