Chunyu Guo

To investigate the evolutionary behavior of the physical and chemical properties of reservoirs following the injection of supercritical CO2, a custom-built constant temperature and pressure supercritical CO2-water-rock heat flow curing coupling experimental system was used to conduct supercritical CO2 soaking experiments on siltstone. The changes in cation concentration within the reaction solution were analyzed, and the evolution of the porosity, permeability, and water/gas saturation of the reservoir core samples was examined before and after the reaction; the experimental results were compared with numerical simulations. The reaction rate constant and activation energy were adjusted, and a method for eliminating the error associated with the time effect on the reservoir’s physical and chemical properties during CO2 geological sequestration was proposed. Additionally, the long-term changes in the physical and chemical properties of the reservoir during prolonged supercritical CO2 sealing were examined. The results indicate that with prolonged exposure to supercritical CO2, the pH of the reaction solution decreases from 7.19 to 5.68. Calcite had the fastest dissolution rate, followed by potassium feldspar and, finally, Illite. During CO2 injection, both the porosity and permeability of the reservoir increased rapidly, but the increase was smaller after CO2 injection ceased, eventually stabilizing. The time-dependent behavior of the physical and chemical properties of siltstone under supercritical CO2 conditions was determined, providing valuable insights into the pore permeability characteristics of reservoirs under long-term mineralization.