Impact of wettability and injection rate on CO₂ plume migration and trapping capacity: A numerical investigation

Rock wettability at prevailing subsurface conditions plays an important role in the fate of injected CO₂ in terms of the trapping capacity and containment security. While several laboratory investigations evidenced the influence of wettability on CO₂ storage potential, still the associated field-scale storage capacity predictions received little or no attention and thus remain poorly understood. This is particularly true for sandstone formations where recent evidence has shown a remarkable variability in their wetting behavior e.g. ranging from strongly water-wet to even CO₂-wet (in the presence of naturally occurring organic acids). In this work, we perform a series of field-scale numerical simulations to examine the impact of variable sandstone/CO₂/brine system wettability on residual and solubility trapping of CO₂. Furthermore, the influence of injectivity on the CO₂ plume migration behavior and trapping capacity is also analyzed and reported. The results indicate that CO₂ plume migration and storage efficiency are a strong function of wettability and injection rate. The water-wet sandstone system demonstrated 42 % higher residual trapping compared to CO₂-wet sandstone – suggesting a notable impact. Moreover, 94 % lower mobile CO₂ and ∼ 20 % less dissolved CO₂ were observed in water-wet sandstones – attributed to strong residual trapping capacity and smaller interfacial brine/CO₂ area. An increase in injection duration resulted in a monotonous decrease in residual trapping and an increase in the solubility trapping and plume migration distance. Higher injection rates led to increases in migration distances and trapping capacities.