Study On The Influencing Mechanism Of Viscosity Variation Of Waxy Crude Oil Emulsion Under Magnetic Treatment

Magnetic treatment technology can change the rheological properties of crude oil and emulsions,which is beneficial to the viscosity reduction and oil-water separation.Based on theories such as petrochemistry and magnetic physics,the study investigates the relationship between the viscosity of emulsion and magnetic treatment conditions through static magnetic treatment experiments and molecular dynamics simulations.The viscosity reduction mechanism of magnetically treated emulsions is revealed,which provides a scientific basis for the application of magnetic technology.To meet the needs of experiments,the static electromagnetic treatment device was designed and developed,which can generate a direction-controlled,high-voltage directdriven,high-efficiency alternating magnetic field.The experimental study concludes that the magnetic treatment temperature has a key influence on the viscosity reduction effects of emulsion.When the magnetic treatment temperature is WAT,the viscosity of emulsion changes from increase to decrease after applying permanent magnet,and the decreasing rate of viscosity is stable and more than 10% at high magnetic field strength.When the magnetic field is applied below WAT,the viscosity of the emulsion decreases.By comparing the changes of droplet size and oil-water interfacial tension before and after magnetic treatment,it is concluded that the magnetic field fails to significantly change the particle size distribution of emulsion droplets.When the permanent magnetic field is applied and the magnetic treatment temperature is WAT,the interfacial tension of emulsion decreases under high magnetic field intensity and increased under low magnetic field intensity.When electromagnetic magnetic field is applied and the magnetic treatment temperature is above WAT,the interfacial tension increases,and it increases with the increase of magnetic field frequency.To investigate the effect of waxes and asphaltenes on magnetic viscosity reduction,molecular dynamics simulations of the interface of emulsion under magnetic field are carried out.By comparing the simulated values of interfacial tension and other properties with experimental values,the 1.2*CM5 charge model,SPC/E water model and OPLSAA force field are determined as the best simulation conditions.By modifying the Velocity-Verlet algorithm,the magnetic field can be applied to non-metallic atoms with arbitrary charge values,which overcomes the limitation of different Larmor frequencies of atoms in the charge model.This method is not limited to relying on charge grouping to apply the magnetic field,which has a wider application.Based on the molecular dynamics simulations of the interfacial properties of emulsions under magnetic field,the results show that the distribution of asphaltenes at the interface becomes more aggregated,and the binding of asphaltenes and water molecules is enhanced.The polar components significantly affect the viscosity reduction after magnetic field.For the system without wax molecules,the interfacial tension decreases after applying magnetic field.But for the system with waxes,the interfacial tension increases and the interfacial energy increases.The magnetic field increases the diffusion coefficients of molecules,enhances the mobility,promotes the adsorption of paraffin molecules at the oil-water interface,which weakens the spatial resistance of light oil molecules and reduces the viscosity of oil phase.The changes in oil phase viscosity and oil-water interface energy are the underlying causes of the changes in emulsion viscosity under magnetic field.