Synthesis of biopolymer nanocomposites and experimental investigation on enhanced oil recovery

Nanoparticles (NPs) are widely used in the petroleum industry, particularly in upstream and downstream applications, due to their quantum effects and high surface area-to-volume ratio. However, stable dispersion and high input ratios of NPs are critical factors limiting their application. This study thus synthesizes the biopolymer nanocomposite E-Ag NPs in one step using the metabolic product exopolysaccharide (EPS) from Bacillus subtilis as both a reducing and stabilizing agent. This study explored the potential of E-Ag NPs to enhance oil recovery in low- and medium-permeability formations. Experimental results showed that the average particle size of Ag NPs synthesized using EPS ranged from 20 to 50 nm. The presence of EPS resulted in a higher Zeta potential value (−43.4 mV), indicating improved stability of the nanofluid, effectively inhibiting NPs aggregation. Interfacial tension and wettability evaluation experiments demonstrated that E-Ag NPs exhibited excellent capabilities in reducing interfacial tension and altering wettability. In the enhanced oil recovery evaluation experiments, the imbibition experiment with E-Ag NPs achieved a maximum recovery rate of 54.32%, and the core flooding experiment reached a maximum recovery rate of 16.33%. In conclusion, the biopolymer nanocomposites developed by this method offer valuable guidance and reference for oilfield development, providing a green and efficient potential solution for enhanced oil recovery.