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 (CO2EOR) 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 & sdot;min & sdot;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.