The sealing integrity of caprock is crucial for the long-term security of geological CO2 storage, yet the multifactorial controls on CO2 breakthrough pressure and its evolution under CO2 exposure remain insufficiently understood. Using caprock samples from the Ordos Basin, this study combined stepwise pressure elevation experiments, NMR, and CT to investigate the effects of temperature, core length, water saturation, and permeability on CO2 breakthrough pressure and to reveal associated pore–throat evolution. Results show that breakthrough pressure increases with temperature and water saturation but decreases with permeability and exhibits an approximate linear relationship with core length, with permeability being the dominant controlling factor. Furthermore, CO2–water–rock reactions lead to a “pore expansion-plugging” pattern, which significantly reduces breakthrough pressure and weakens sealing capacity, though this weakening stabilizes over time. These findings clarify the key controls and time-dependent evolution of caprock sealing, providing a theoretical basis for assessing storage security and predicting long-term efficacy in depleted reservoirs.
Jia et al. (Fri,) studied this question.