Study on Corrosion Law and Corrosion Life Prediction of Tubular String in CO2 Huff and Puff Well

Abstract Taking into account the process characteristics of CO2 injection wells, which involve low-temperature injection, long-term sealing, rapid depressurization, and continuous production, the FLUENT software was adopted to simulate and calculate the wellbore temperature, pressure and CO2 phase distribution at each stage of typical Wells, and the corrosion laws of corrosion of the tubing string during the entire CO2 injection process were studied through corrosion simulation experiments. The CO2 corrosion rate prediction model and the API TR 5C3 standard were adopted to calculate the corrosion rate of the entire wellbore string at each stage and the remaining strength of the string after corrosion. Based on the corrosion rate and the remaining strength of the string, a prediction method for the remaining corrosion life of the wellbore string throughout the entire process was established. The research results showed that in the four stages, the phase states of CO2 undergo phase change at 1070m, 796m, 777m, and 462m respectively. The corrosion rate of the wellbore string in each stage was pressure release > well confinement > production > gas injection. In the same stage, with the increased of well depth, the corrosion rate of the string increased significantly. Due to the long duration of the production stage and the large cumulative corrosion amount, the maximum thinning amount within one throughput cycle reached 0.84mm, which was the main stage where corrosion occurs. Without taking anti-corrosion measures, the minimum service life of the oil well tubing string in typical Wells was only 8 months. The prediction results provided a theoretical basis for determining the limit of throughput cycles.