Synthesis of amphiphilic Fe3O4@CS/CTAB core shell nanocomposites for enhanced oil recovery via interfacial tension reduction and wettability alteration

Capillary entrapment and oil wet reservoir rocks severely limit the ultimate recovery of crude oil during conventional water flooding processes. This study aims to engineer a highly stable amphiphilic Iron(III) oxide@chitosan/cetyltrimethylammonium bromide (Fe 3 O 4 @CS/CTAB) core shell nanocomposite to significantly enhance secondary and tertiary oil recovery by reducing dynamic oil water interfacial tension and altering rock wettability. The core shell nanoparticles were synthesized via chemical coprecipitation followed by chitosan encapsulation and cetyltrimethylammonium bromide functionalization. Comprehensive characterizations including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDS) confirmed the successful grafting and structural integrity of the 14.5 nm crystalline magnetite cores. Colloidal stability tests identified 1000 ppm as the optimal concentration ensuring prolonged thermodynamic dispersion. Experimental evaluations demonstrated that the nanofluid drastically reduced the interfacial tension to 1.8 mN/m and shifted the heavily oil wet sandstone contact angles from 158 degrees to a strongly water wet state of 31.10°. Dynamic core flooding experiments validated these static findings where a sequential tertiary injection strategy yielded ultimate recovery factors of 73.4% and 70.3% for low and high acidic crude oils respectively. In summary the engineered nanocomposites effectively mobilize trapped residual oil through synergistic structural disjoining pressure and electrostatic interactions proving to be highly efficient agents for advanced enhanced oil recovery applications. Clinical trial number: Not applicable.