Thermo-hydraulic behaviour of compressed flue gas storage in aquifers

A system for compressed flue gas energy storage in aquifers is proposed, combining compressed gas energy storage with carbon dioxide (CO2) sequestration. Transient simulations of the cyclic injection-production process in aquifers with anticlinal symmetric structures were conducted, incorporating the flow, phase, saturation, and chemical reaction equations. The dynamic characteristics of bottom-hole pressure, bottom-hole temperature, and the gas-phase saturation field under designed operating conditions were analysed. The total carbon dioxide storage capacity throughout the dynamic process was calculated. Energy and exergy efficiencies of the compressed flue gas in a single injection-production cycle were also evaluated. The results show that over time, bottom-hole pressure, temperature, and gas-phase saturation fields gradually stabilise into periodic patterns during the cyclic injection-production process. Carbon dioxide storage capacity increases continuously, while energy efficiency declines before stabilising, and exergy efficiency rises before stabilising. The effects of gas storage construction duration and injection-production rates on the dynamic characteristics of the cyclic process were also examined. Longer construction durations result in smaller bottom-hole pressure and temperature differences during injection-production, higher carbon dioxide sequestration, and improved exergy efficiency in the Huff-n-Puff operation. Conversely, higher injection-production rates lead to greater bottom-hole pressure and temperature differences and increased carbon dioxide sequestration, but lower exergy efficiency in the Huff-n-Puff operation.