To overcome the problems of large dosage, fast sedimentation, and the unsatisfactory emulsification effect of traditional magnetic nanoparticles, polymer-modified magnetic nanoparticle Co3O4@HPAM was synthesized as an emulsifier for heavy oil O/W emulsion by modifying the surface of Co3O4. The composition of Co3O4@HPAM was characterized by Fourier transform infrared spectroscopy, X-ray diffraction analysis, thermogravimetric analysis, and scanning electron microscopy. Then, the effects of the mass fraction of magnetic nanoparticles before and after modification on the stability and rheology of the emulsion were compared and analyzed. The experiments show that the degree of reduction of the water-separation rate under the action of Co3O4@HPAM was 13 times higher than that under the action of Co3O4 at the same mass fraction. By using Co3O4@HPAM, the water separation of the emulsion was only 6.74% at 4 h, while the viscosity reduction was greater than 97% at a mass fraction of 0.04%. Finally, combined with the test results of zeta potential, interfacial tension, contact angle, and oil droplet distribution, the effect mechanism of Co3O4@HPAM on the viscosity reduction of heavy oil emulsification was investigated. It is found that the polymer-modified magnetic nanoparticles have stronger negative electricity, a larger contact angle, and smaller interfacial tension, while the oil droplets under their action have a smaller radius and a more homogeneous distribution. The research in this paper provides a theoretical basis for the application of magnetic nanoparticles in heavy oil emulsification and viscosity reduction technology.
To improve the dispersibility and emulsification performance of magnetic nanoparticles, this study first synthesized three modified magnetic nanoparticles (Co 3 O 4 @HPAM) with different monomer ratios and characterized their physical properties. On this basis, the effects of the modified magnetic nanoparticles with different monomer ratios on the emulsification and viscosity reduction of thick oil were investigated by stability and rheology; finally, the emulsification and viscosity reduction mechanism was revealed by combining the zeta potential, surface tension, contact angle, and oil droplet distribution. The results showed that Co 3 O 4 @HPAM with three different monomer ratios was successfully synthesized and exhibited good dispersibility. With the increase of monomer ratio, the emulsion water fraction decreased first and then increased, and the viscosity reduction decreased first and then increased. At a mass fraction of 0.04%, the sample with a 15% monomer ratio exhibited the lowest water separation rate (6.45% at 4 h) and the highest viscosity reduction rate (97.93%). This phenomenon occurs because, at a 15% monomer ratio, the modified magnetic nanoparticles have a higher negative charge, a larger contact angle, lower oil-water interfacial tension, and smaller, more uniformly distributed oil droplets. This study offers a theoretical foundation for using magnetic nanoparticles in heavy oil emulsification to reduce viscosity.
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