Underwater self-healing and highly stretchable nano-cellulose composite hydrogels based on dipole-dipole interactions for a "smart" plugging in CO2 flooding.

The development of hydrogels with water resistance, superb self-healing and mechanical performance that can adapt to the reservoir conditions to plug CO₂ channeling in reservoirs has a significant potential to boost the enhanced oil recovery and CO2 geo-sequestration. Herein, we present underwater self-healing and highly stretchable nano-cellulose composite hydrogels for plugging in CO2 flooding via in situ polymerization of acrylonitrile (AN) based solution with carboxyl-grafted nanocellulose (TOCNF) and tannic acid (TA), which exhibited a Young's modulus of 1.1 MPa, a stretchability of 1624 % and a toughness of 13.22 MJ/m3. The presence of dipole-dipole interactions between the CN groups of the copolymer chains endowed this gel with excellent underwater repair with 98.9 % self-healing efficiency within 48 h. In the artificial porous media, the PAMN-TA-TOCNF systems (including the in-situ gel and the preformed particle gel) demonstrated remarkable efficacy and renewable plugging performance, which is attributed to their pore-scale remigrating behaviour (i.e., capture, healing-to-trapping, elastic deformation, and frictional migration). This "smart" gel could provide an environment-friendly and remarkably economic (no disposable) alternative to the current state of the CO2 plugging project in oilfields.