Experimental Investigations and MD Simulation on Nanoparticle-Enhanced CO₂-Responsive Foam (NECRF): Implications on CO₂-EOR

CO 2 -responsive foam (CRF) is a highly promising candidate for CO 2 -enhanced oil recovery (CO 2 -EOR) because it displays higher stability than the surfactant-stabilized foam owing to the formation of robust wormlike micelles (WLMs) upon exposure to CO 2 . In this work, the nanoparticle-enhanced CO 2 -responsive foam (NECRF) was properly prepared using lauryl ether sulfate sodium (LES)/diethylenetriamine/nano-SiO 2, and its interfacial properties and EOR potential were experimentally and numerically assessed, aiming to explore the feasibility and effectiveness of NECRF as a novel CO 2 -EOR technique. It was found that the interfacial expansion elastic modulus increased 6-fold after CO 2 stimulation. The modulus continued to increase with the introduction of nano-SiO 2 owing to the pronounced synergistic effect of WLMs and nanoparticles. In addition to increasing the viscosity of the foaming liquid, WLMs and nano-SiO 2 enhanced the shearing resistance of the NECRF as well. Calculations demonstrated that both the coarsening rate and the size distribution uniformity coefficient of NECRF were markedly lower than that of the LES foam, which subsequently inhibited NECRF decay and greatly improved its dynamic stability. Besides, molecular dynamics simulation revealed that adding inorganic salts to NECRF could notably enhance the foaming performance due to the intensified hydration of surfactant head groups and reduced binding energy of neighboring molecules. Nuclear magnetic resonance-assisted core flooding experiments validated the exceptional capacity of NECRF to sweep the low-permeability region and improve the conformance profile. Overall, these findings may provide valuable insights into the development and application of novel materials and strategies for the CO 2 -EOR.