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

Abstract

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.