Coupled Temperature–Pressure Prediction in CO2 Injection Wells During the Carbon Capture and Storage Process

In carbon capture and storage (CCS) systems, the wellbore serves as a critical connecting channel between CO2 surface capture facilities and underground storage formations. Accurate prediction of the temperature, pressure, and physical properties of CO2 fluid within the wellbore is essential for its safe sequestration. In this study, a coupled temperature–pressure-phase prediction model for CO2 injection wells is established based on the conservation laws of mass, energy, and momentum, combined with the PR-TWU equation of state. The maximum errors in temperature and pressure for the CO2 injection case well are only 4.57% and 2.05%, respectively, verifying the accuracy of the model. The distribution and variation in temperature, pressure, and physical property parameters in the CO2 injection wellbore are systematically investigated. The results show that with increasing well depth, the temperature, pressure, and flow velocity of CO2 fluid exhibit an increasing trend, while its density and viscosity gradually decrease. During CO2 injection, the well depth at which the CO2 phase transition occurs is closely related to the critical temperature of CO2 (31.04 °C). Wellbore pressure is mainly controlled by injection pressure, whereas injection temperature and injection rate are the key parameters affecting wellbore temperature and CO2 phase transition. The findings can provide a theoretical basis for the optimization of injection parameters and the integrity evaluation of CO2 sequestration injection wells.