The Influence of Heterogeneity in Wettability and Pore Structure in CO2 Geological Sequestration: A Pore-scale Study

Owing to the complexity of geological formation, a detailed understanding of all transportation phenomenon of CO2/water in porous media occurring in CGS is not yet gained. Heterogeneity in wettability and pore structure exists in mostly natural geological formation which has been proof that gives strong effects on porous media flow. Since macroscopic transportation phenomenon in porous media are always determined by pore-scale properties, investigation on heterogeneity at pore-scale gives the most fundamental influence mechanisms of heterogeneity in wettability and pore structure. In this study, we reported a pore-scale study on the influence of heterogeneity in wettability and pore structure in vertical CO2/water displacement experiments using a micro-CT machine. Two stratified sand packs, BZ06+BZ02, quarz+dolomite, were employed in displacement experiments. The experiment results indicate that, CO2 saturation pattern shows a big difference between dolomite layer and quartz layer, CO2 enters more pore spaces and owns higher CO2 saturation in dolomite layer than quartz layer in drainage. While in glass beads pack, it is noticeable that the capillary barrier of BZ02 layer significantly affects CO2 percolation process. CO2 occupied little void volume of BZ02 porous matrix. In imbibition, residual CO2 was mainly trapped in more wetting quartz layer in quartz+dolomite pack, and more compact layer in BZ06+BZ02 pack.