An intelligent CO2-responsive hydrogel for applications in enhanced oil recovery and CO2 geological storage

A novel CO₂-responsive hydrogel for intelligent control of gas channeling in CO₂– enhanced oil recovery (CO₂-EOR) and geological CO₂ storage has been developed. A monomeric long-chain tertiary amine surfactant (HXB-2) that has specific amide and carboxyl groups was synthesized. The surfactant can interact with CO₂ in aqueous solution to increase the viscosity and induce gelation. The hydrogel is irreversible and does not revert to solution phase after N₂ bubbling. It shows excellent structural stability and thermal resistance and the viscosity remains four times higher than that of the initial solution upon heating. For the mechanism, HXB-2 protonates in CO₂ environment and self-assembles into worm-like micelles (WLMs) under synergistic forces of hydrophobic interaction, hydrogen bonding, and electrostatic interaction, which further crosslink to form a three-dimensional (3D) network to induce gelation. The hydrogel can be formed in-situ to control gas channeling intelligently and redirect the gas to unswept low-permeability channels. It can enhance the recovery rate by 23.53 % and the maximum seepage resistance reaches 29.45 MPa·min·cm⁻³ for water-alternatinggas flooding. Moreover, by having spontaneous association and shear-dissociation properties, the hydrogel in the rock pores causes minimal damage to the reservoir. This study provides valuable insights and empirical support for the development of irreversible CO₂-responsive hydrogels for CO₂ chemical sequestration and gas channeling control to help EOR and geological CO₂ storage.