Experimental study on the emulsification and interfacial properties of modified nano-silica fluids: Effects of fatty acids, dicarboxylic acids, fatty amines, and aromatic acids

The low permeability and strong heterogeneity of low-permeability reservoirs result in low recovery rates from water flooding, making it challenging for conventional methods to effectively extract crude oil. Nano-SiO 2 , with its advantages of small particle size, low cost, and ease of modification, has garnered significant attention in the field of enhanced oil recovery. This study systematically investigates the emulsification performance, interfacial tension, and interfacial viscoelasticity of nano- SiO 2 modified with fatty acids, fatty amines, and aromatic carboxylic acids through multiscale experimental methods, revealing the structure-property relationships between the modifier’s molecular structure and the resulting interfacial performance. The experimental results demonstrate that the modified nano-SiO 2 significantly enhances emulsion stability and interfacial activity. Notably, the benzoic acid-modified nano-SiO 2 exhibits the best performance, achieving an internal phase inversion point (IPIP) of 85 %, reducing interfacial tension to 5.61 mN/m, and yielding a comprehensive modulus of 25.26 mN/m. The carbon chain length, functional group type, and number of aromatic rings significantly influence emulsification performance and interfacial tension. Composite modification with benzoic acid and dodecanoic acid (4:1) further optimizes emulsion stability. This study provides a theoretical foundation and technical support for developing efficient and stable nano-emulsifiers, offering new strategies for enhancing oil recovery in low-permeability reservoirs.