Dual-functionality of CO2-responsive ionic liquids for CO2 storage: Fatty acid particles re-precipitation and clay swelling inhibition

Gas channeling during CO 2 flooding presents a significant challenge to the effective underground storage of CO 2 . This study introduces a novel gas channel blocking strategy using the phase transition properties of fatty acid based CO 2 -responsive ionic liquids (ILs). The ILs were synthesized from choline hydroxide (Ch) and high-melting-point fatty acids (FA), including myristic acid (C14) and palmitic acid (C16), named FA-Ch ILs. These ILs demonstrate phase transformation behavior after CO 2 injection, leading to the precipitation of FA as solid particles. The FA-Ch ILs aqueous solution exhibits low viscosity, ensuring excellent injectivity for oilfield applications. After CO 2 injection, the precipitated FA particles act as gas channeling plugging agents, while the protonated Ch ions effectively inhibit clay swelling to enhance oil recovery with a synergistic effect. Structural properties and interaction mechanisms of the FA-Ch system were characterized by FT-IR, 1 H NMR, and molecular dynamics simulations. The particle size of the FA precipitates was regulated by adjusting FA-Ch concentration and CO 2 injection rate to make it suitable as a profile control agent. Furthermore, Ch + ions demonstrate clay swelling inhibition comparable to traditional inhibitors like KCl. This dual-functionality positions FA-Ch ILs as an innovative solution for addressing gas channeling and clay swelling in CO 2 flooding, offering a cost-effective and environmentally friendly alternative to conventional methods.