CO2-Resistant Nano-Reinforced Gels for Effective Gas Channeling Control in CO2 Geological Utilization

CO2 flooding technology can effectively enhance oil recovery in low-permeability reservoirs while offering significant potential for CO2 geological sequestration. However, high-permeability zones and micro-fractures within reservoirs often lead to gas channeling, thereby reducing the efficiency of CO2 utilization. In this study, a CO2-tolerant crosslinked polymer gel system was developed as a potential solution to mitigate gas channeling. By incorporating nanoparticles into the gel network, the stability of the gel in CO₂ environments was significantly improved. A CO2-resistant polymer was first synthesized using acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and dimethylaminoethyl methacrylate as functional monomers. This polymer was then mixed with nano-silica and crosslinked with hexamethylenetetramine (HMTA) and hydroquinone to construct a robust viscoelastic gel network. The optimized formulation of the CO2-resistant nano-reinforced gel was determined to be: 0.5% CO2-resistant polymer + 0.4% HMTA + hydroquinone + 0.2% nano-silica. Under CO2 conditions of 90 °C and 15 MPa, the CO2-resistant nano-reinforced gel exhibited excellent anti-aging performance, with its elastic modulus increasing from 16.04 Pa to 24.99 Pa. Core flooding laboratory experiments and field trials confirmed its gas-blocking capability. After CO2 exposure, the residual resistance factor increased from 32.78 to 45.24, the breakthrough pressure gradient rose from 25.36 to 40.25 Pa. The gas channeling development coefficient is reduced to 0.78. The injection pressure in field applications reached 25.4 MPa, all of which significantly outperformed conventional gels. The results indicate that this CO2-resistant nano-reinforced gel possesses excellent CO2 resistance and gas-blocking performance, providing an effective technical solution to address gas channeling issues during CO2 geological utilization.