Hysteresis Implications for Long-Term Underground CO₂ Storage

The injection of CO₂ into geological formations is a promising strategy for carbon sequestration. However, the CO₂ storage containment can be significantly influenced by the complex dependence of capillary pressure and relative permeability on the saturation path and history (hysteresis) within the porous media. Thus, understanding hysteresis effects is critical to accurately estimating CO₂ storage capacity. This study quantifies how hysteresis alters saturation profiles and residual trapping in geological formations during and after CO2 injection, emphasizing its role in improving confidence in the CO₂ migration path, capillary trapping, residual trapping, and finally plume shape, through a numerical model.
For this study, a conceptual model is built, focusing on the impact of the hysteresis on CO₂ migration path and plume shape and size. Since reservoir characteristics have a notable effect on flow behaviour within porous media, this study investigates the plume shape, size and migration path in 3 different rock types namely tight, medium, and good sand, simultaneously (Figure 1). The results demonstrate that neglecting hysteresis can lead to inaccurate predictions of CO₂ plume shape, residual trapping capacity, and breakthrough times (Figure 2). Results also show that when considering the hysteresis, there is a reduction in residual trapping while capillary trapping increases. Furthermore, hysteresis implication is shown to critically affect fluid distribution and CO₂ immobilization (capillary trapping) in heterogeneous formations. Understanding the effect of hysteresis implication in CO2 storage is essential for optimizing injection strategies and ensuring long-term storage security which resulted in a more reliable decision making among CO₂ sequestration projects.