Mechanical Behavior around a Wellbore during Injection of Supercritical CO2 into a Low-Permeability Reservoir

Summary Carbon dioxide (CO2) geological storage (CGS) has been regarded as one of the most promising approaches to reduce the concentration of CO2 in the air, and a good understanding of the mechanical behavior around a wellbore during CO2 injection is essential for safe geological storage. In this study, we develop a fully coupled thermal-hydraulic-mechanical (THM) analytical model for predicting constant-rate injection of supercritical CO2 (scCO2) into a porous reservoir. By using the Laplace transformation and imposition principle, analytical solutions in the Laplace domain for the pore pressure, temperature, displacement, strain and stresses are obtained and converted into the values in the time domain via Stehfest inverse Laplace transformation. The numerical results show a linear relationship between the wellbore pressure and the injection rate and high sensitivity of pore pressure to reservoir permeability. Based on this relationship, an analytical formul is proposed to determine the critical breakdown time under constant-rate injection.It is found that the injection rate is the most sensitive parameter controlling the critical breakdown time, which significantly decreases with increasing the injection rate. These findings provide a quantitative tool and theoretical basis for predicting the maximum allowable injection rate, optimizing injection strategies, and assessing wellbore stability risks in CGS projects.