CO2-induced phase separation in ionic liquid aqueous solutions: enhancing CO2 storage capacity in CO2 flooding

Abstract

CO₂ flooding offers dual benefits by enhancing oil recovery and facilitating CO₂ storage. However, reservoir heterogeneity and clay swelling can significantly limit CO₂ storage capacity. Here, a novel strategy for in-situ formation of particle profile control agent and clay swelling inhibitor was established by CO₂-responsive ionic liquids (ILs). Two fatty acid (FA)-based ILs were synthesized by reacting N, N-dimethylcyclohexylamine (DMCHA) with myristic acid (C14) and palmitic acid (C16). After CO₂ injection, FA was precipitated again as a particle profile control agent with a particle size exceeding 10.65 μm, while the protonated DMCHA in the remaining liquid phase serves as a clay swelling inhibitor. Notably, the precipitation of FA within the core increases the CO₂ storage capacity by 1.96 times. This innovative approach holds great promise for enhancing the efficiency and sustainability of CO₂ injection, benefiting both the petroleum industry and environmental protection.