CO₂-triggered self-healing gel based on semi-interpenetrating networks: Innovative mechanism and remarkable repair...

In the context of CCUS-EOR technology applications, the issue of microcrack propagation caused by high-concentration CO₂ corrosion of cement rings is particularly prominent. This study developed a CO₂-responsive semi-interpenetrating network self-healing gel (Ca-AGH) using AM, DMAEMA, and SA as monomers, MBA as a crosslinking agent, and AAPH as an initiator. The gel was synthesized via aqueous solution polymerization and utilized Ca²⁺ coordination with sodium alginate to construct a semi-interpenetrating network structure. Experiments indicate that Ca-AGH exhibits a pyrolysis temperature of approximately 200 °C, with a honeycomb-like surface structure that demonstrates high water absorption and retention capacity. Under optimized conditions, its compressive strength reaches 1444.0 kPa. It exhibits high sensitivity to CO₂ concentration, with a significantly higher equilibrium swelling ratio in CO₂-saturated solutions compared to pure water. Its mechanical properties are enhanced by 10.24 times due to the semi-interpenetrating network structure. Repair experiments showed that when Ca-AGH was added at 2 wt%, the temperature was 80 °C, and the CO₂ pressure was 8 MPa, the repair rate of cement stone reached 96.7% after 21 d, with superior repair effects on microcracks of different widths compared to the control group. Its self-repair mechanism involves the synergistic action of physical expansion sealing and chemical deposition. This study developed a high-strength, CO₂-responsive self-healing gel, effectively addressing the issues of low cement stone strength and limited repair methods caused by existing CO₂-triggered self-healing technologies. It provides an efficient and economical new approach for repairing micro-cracks in cement rings in CCUS-EOR technology.