Laboratory Evaluation of a Novel Self-Healable Polymer Gel for CO₂ Leakage Remediation during CO₂ Storage and CO₂ Flooding

For CO ₂ storage in subsurface reservoirs, one of the most crucial requirements is the ability to remediate the leakage caused by the natural fractures or newly generated fractures due to the increasing pore pressure associated with CO ₂ injection. For CO ₂ Enhanced Oil Recovery (EOR), high conductivity features such as fractures and void space conduits can severely restrict the CO ₂ sweep efficiency. Polymer gels have been developed to plug the leakage and improve the sweep efficiency. This work evaluated a CO ₂ resistant branched self-healable preformed particle gel (CO ₂ -BRPPG) for CO ₂ plugging purpose. This novel CO ₂ -BRPPG can reform a mechanical robust adhesive bulk gel after being placed in the reservoir and efficiently seal fractures. In this work, the swelling kinetics, self-healing behavior, thermal stability, CO ₂ stability, rheology, adhesion property and plugging performance of this novel CO ₂ -BRPPG were studied in the laboratory. Results showed that this CO ₂ -BRPPG has good self-healing abilities, and the self-healed bulk gel has excellent mechanical and adhesion strength. Gel with a swelling ratio of ten has an elastic modulus of over 2000 Pa, and the adhesion strength to sandstone is 1.16 psi. The CO ₂ -BRPPG has good CO ₂ phase stability at 65 °C, and no dehydration was observed after 60 days of exposure to 2900 psi CO ₂ at 65 °C. Core flooding test proved that the swelled particles could reform a bulk gel after being placed in the fractures, and the reformed bulky gel has excellent CO ₂ plugging efficiency. The supercritical CO ₂ breakthrough pressure gradient was 265 psi/feet (5.48 MPa/m). This work could offer the experimental basis for the field application of this CO ₂ -BRPPG in CO ₂ storage and CO ₂ enhanced oil recovery.