Preparation and performance evaluation of nanoparticle plugging agent for CO2 gas channeling control

Carbon dioxide (CO2) flooding is one of the efficacious channels to enhance oil recovery efficiency of low permeability reservoirs. However, CO2 gas channeling has seriously affected the development effect due to severe formation heterogeneity. Nanomaterials have good application prospects in plugging gas channeling, but the dispersibility in water limits the plugging effect. In this paper, a nanoparticle plugging agent with a core-shell architecture was synthesized via emulsion polymerization. The impacts of different elements such as grain diameter, temperature and salinity on the swelling characteristic of nanoparticles were studied respectively. Subsequently, the CO2 response property of nanoparticles was tested by uniformly injecting CO2. Finally, based on the calculation of molecular dynamics, the interaction between nanoparticles and water molecules was analyzed. The results showed that the CO2-responsive nanoparticles exhibit a lower swelling ratio (<5), and the residual resistance coefficient is 2.47, demonstrating a limited expansion property and superior plugging performance. The interaction between protonated nanoparticles and water molecules was stronger, resulting in enhanced hydrophilicity and responsive inflation of nanoparticles. The system has great potential application prospects for in-depth CO2 conformance control.