Impact of Water Alternating Gas and Intermittent Injection on CO₂ Dissolution During CO₂ Sequestration in Saline Aquifers Considering Thermal-Hydraulic Coupling and Thermal-Hydraulic-Mechanical Coupling Effects

Based on TOUGH+ and a more accurate physical property calculation model, a thermal-hydraulic coupling simulation method suitable for CO₂ sequestration in saline aquifers is established. The method was further coupled with RGMS using the fixed-stress split iteration model, improved from the fixed-stress split two-way model, to obtain a more accurate thermal-hydraulic-mechanical iteratively coupling simulation method. Based on the geological characteristics of the Ordos Basin, a geological model is constructed, and the thermal-hydraulic and thermal-hydraulic-mechanical coupling simulation methods mentioned above are used to simulate the process of CO₂ dissolution during CO₂ sequestration in saline aquifers. The impacts of water alternating gas injection and intermittent injection schemes on CO₂ dissolution, pore pressure, and formation deformation are investigated. The following results are found: the thermal-hydraulic-mechanical iteratively coupling model can better assist in designing more reasonable injection schemes; only water alternating gas injection can enhance CO₂ dissolution; intermittent injection contributes to the recovery of pore pressure and formation deformation. The results can provide theoretical guidance for the CO₂ sequestration in saline aquifers by CO₂ dissolution.