A CO ₂ -Responsive Gel System (AM/NVP/DMAEMA) for Plugging High-Permeability Gas Channeling Zones in a CO ₂ Flooding Process

To address the issue of CO₂ channeling along high-permeability zones during the development of CO₂ flooding in low-permeability reservoirs, this study developed a CO₂-responsive gel system for gas channeling plugging. Through molecular design, a CO₂-responsive polymer (AM/NVP/DMAEMA) was synthesized, and its structure was characterized. The results indicated that the successful synthesis of the polymer was confirmed. Constructed based on this CO₂-responsive polymer (AM/NVP/DMAEMA), the CO₂-responsive polymer gel system (designated as DKS) has the following formulation: the CO₂-responsive polymer with a mass fraction of 0.5%, WD-1 with 0.8%, and WD-2 with 0.8%. Performance tests of DKS were conducted under relevant environmental conditions (e.g., different temperatures, salinities, and pressures). The results showed that the gelation strength of the system is above grade H with an elastic modulus (<i>G</i>') > 2 Pa; after 30 days of aging, the gel strength remains above grade H, and the water loss rate after 30 days of aging is <5%. In the CO₂ flooding simulation experiment on artificial cores, DKS exhibited excellent injectability and plugging performance: the injection pressure is below 0.80 MPa, the plugging rate can reach over 95%, and the reduction rate of the CO₂ outlet flow can reach over 95%. In a CO₂ atmosphere, compared with conventional gels, DKS demonstrates outstanding gel strength and stability in CO₂ environments, which holds a significant reference value for the efficient development of CO₂ flooding in low-permeability reservoirs.