摘要：During CO 2 injection into deep saline aquifers, the overlying caprock may be subjected to geochemical reactions which can alter the leakage pathways for injected CO 2 . Thus, it is crucial to identify the supercritical CO 2 (scCO 2 ) flow behaviour via fractures in caprock and its permeability to estimate the permanence of injected CO 2 . The objective of this study is to find the effect of scCO 2 flow on fractured caprock permeability. A fractured siltstone sample was saturated in deionized water and conducted scCO 2 permeability tests using a high-precision advanced core flooding apparatus under different injection pressures and confinements. Next, the siltstone sample was saturated in 10% w/w NaCl brine and conduced scCO 2 permeability tests as described earlier. The results show that the brine-saturated sample has low permeability compared to water-saturated siltstone sample. The reason would be the deposition of evaporites during scCO 2 flow through the fractured sample. This is known as CO 2 dry-out phenomenon or absorbing moisture into the scCO 2 , making the remaining brine saturated with salts. Thus, the CO 2 back-migration through the caprock discontinuities becomes minimized due to CO 2 dry-out phenomenon, which is an advantage for the caprock integrity in deep saline aquifers. In addition, aquifers with high salinity contents show significant dry-out phenomenon because pore fluid easily becomes supersaturated with salts due to evaporation of moisture into the scCO 2 .
