Research on Phase Transition and Flow Characteristics of Tubing Leakage in CO₂ Injection Wells

Over the past decade, with the increasing number and scale of Carbon Capture and Storage (CCS) projects internationally, the integrity of CO₂ injection wells has brought growing concern. The downhole tubing is highly susceptible to corrosion and perforation due to factors such as high-pressure low-temperature injection and CO₂ corrosion, which can subsequently lead to wellbore integrity failure. This study employs the Computational Fluid Dynamics (CFD) software Fluent to establish a CFD model for investigating the leakage flow characteristics of downhole tubing in CO₂ injection wells. This model incorporates NIST-based CO₂ property equations, which accurately capture the depressurization phase transition and gas-liquid coexistence phenomena during the leakage process. By studying the flow characteristics of tubing leakage in CO₂ injection wells, this paper reveals the variation patterns of temperature, pressure, and flow velocity during the transient leakage process. The research findings provide a foundation for understanding the flow characteristics of tubing leakage in CO₂ injection wells, supporting the safe and long-term effective operation of CCS projects.

Keywords: CO₂ injection wells, Tubing leakage, Phase transition, Leakage hole diameter, Integrity of CO₂ injection wells, Flow characteristics.