Temperature–Pressure–Time Dependent Microstructural Evolution of Caprock during CO2 Geological Storage: An Experimental Study Integrating CT Scanning and Pore Network Analysis

Abstract The properties of the caprock critically influence the sealing performance of CO 2 geological storage systems. This study systematically investigates the microstructural evolution and stability of caprock under CO 2 exposure, using high-precision computed tomography scanning combined with a factorial experimental design that incorporated temperature and pressure, with a supplementary time-extension experiment. Rock samples from the Chang4+5 layer of the Ordos Basin were characterized in three dimensions before and after reaction. The results demonstrate that CO 2 storage increases porosity and permeability, generating “branch-like” or “root-like” dissolution networks that compromise rock integrity. Temperature elevation significantly accelerates mineral dissolution kinetics, promoting pore expansion and enhancing pore-throat connectivity. Increased pressure enhances CO 2 solubility and diffusivity in pore fluids, intensifying localized acidification and heterogeneous dissolution with a particular effect on throat-scale structural adjustments. Prolonged exposure drives the progressive advancement of the dissolution front and the gradual merging of isolated pores, facilitating the formation of continuous dissolution channels. These findings elucidate the coupled interaction mechanisms between CO 2 and caprock, providing both experimental evidence and theoretical support for site integrity assessment and long-term storage safety evaluation. This work provides direct support for site selection and the advancement of carbon dioxide capture, utilization, and storage technology.