The role of Capillary Hysteresis in Enhancing CO₂ Trapping Efficiency and Storage Stability

Background: The intensifying impact of climate change demands innovative approaches to reduce atmospheric CO₂ levels. Carbon Capture and Storage (CCS) offers a viable solution by sequestering CO₂ in geological reservoirs. However, understanding the role of capillary hysteresis in CO₂ trapping is critical for optimizing CCS performance. Aim: This study aims to investigate the influence of capillary hysteresis on CO₂ trapping efficiency in saline aquifers using detailed simulation models and varying hysteresis values. Materials and methods: Advanced CMG simulation software was utilized to model CO₂ injection and migration in saline aquifers spanning depths of 1200–1300 meters. The model, initially saturated with brine, applied water-alternating-gas (WAG) injection at hysteresis values of 0.2, 0.3, 0.4, and 0.5 to evaluate their effect on CO₂ trapping efficiency. Results: The simulations demonstrated a direct positive correlation between hysteresis values and CO₂ trapping efficiency. At a hysteresis value of 0.5, nearly 100% CO₂ trapping was achieved. This increased efficiency was attributed to stronger capillary forces immobilizing CO₂ more effectively and reducing mobility towards caprock, thereby minimizing leakage risks. Conclusion: The study highlights the key role of capillary hysteresis in enhancing CO₂ sequestration. Higher hysteresis values improve long-term storage stability, emphasizing the need for optimized WAG injection strategies in CCS applications.