The urgent challenge of climate change, driven by rising carbon emissions, necessitates innovative strategies for carbon capture
and storage (CCS). This study examines the impact of hysteresis in relative permeability on CO2 entrapment efficiency within
saline aquifers, known for their significant storage capabilities. An aquifer model was analyzed through numerical simulation by
varying hysteresis values from 0.2 to 0.5 to evaluate their impact on CO2 plume behavior, retention during water-alternating-gas
(WAG) injection, and plume morphology. The CO2 plume exhibits a funnel-shaped configuration at low hysteresis with a narrow,
pointed base, indicating a concentrated upward migration trajectory. In contrast, a hysteresis value of 0.5 results in diminished gas
movement toward the upper aquifer, transforming the plume into a more oval shape. Results from the land trapping model further
support our findings, revealing an inverse relationship where increased hysteresis enhances residual CO2 entrapment, reflected
in trapping coefficient values ranging from 0.5 to 4. This underscores the model’s efficacy in verifying gas trapping efficiency and
safety during sequestration. Moreover, increased water flow generates stronger forces, pushing CO2 into narrower pore spaces,
where it becomes trapped. Our findings indicate that increased hysteresis enhances CO2 retention by limiting vertical migration
and significantly influences plume geometry, promoting stable and predictable distribution patterns. At higher hysteresis values,
CO2 migration is significantly restricted, resulting in near-complete immobilization of the injected gas. This research highlights
hysteresis’s critical role in refining injection methodologies and enhancing plume stability for long-term CO2 storage.