Abstract: In certain mature oilfields that have entered the late high water cut stage, the CO₂ huff-and-puff process can be implemented as a supplementary measure during waterflooding for enhanced oil recovery. This process has led to an increased CO₂ content in the produced water, which can cause severe corrosion in wellbore columns. Thus, the strength of wellbore and casing columns is reduced, leading to pitting corrosion or even column fractures. Therefore, based on the thermodynamic and kinetic principles of electrochemical corrosion and relevant theories of column mechanics, and considering the influences of temperature, pressure, water cut, CO₂ partial pressure, flow rate, deflection angle, and pH based on actual operating conditions at the site, a corrosion prediction model was used to calculate the corrosion rates of a CO₂ huff-and-puff well at different stages of the huff-and-puff process. Methods for calculation of the post-corrosion residual strength and the maximum number of huffand-puff cycles were established. A large number of simulation calculations were performed to predict the casing corrosion patterns and residual wall thickness of the huff-and-puff well under gas injection, soaking, pressure release, and production conditions, as well as the maximum number of huff-and-puff cycles for the well.

Key words: casing, CO₂ huff and puff, CO₂ corrosion, residual strength, maximum number of huff-and-puff cycles