Research On Demulsification Technology Of Oil-water Emulsion Under The Coupling Of Electric Field And Magnetic Field

With the oil field development entering the middle and late stage,various EOR technologies are widely applied,and the difficulty of deep dehydration of crude oil is greatly increased.Electric demulsification technology is to use external electric field to make small droplets in oil-water emulsion coalesce into large droplets,thus realizing settlement separation.There are some problems with existing electric dehydration equipment such as electric field collapse and unstable operation.The combination of electric demulsification and other demulsification technologies has become a new exploration hotspot.Magnetic treatment technology is easy to operate,stable and profitable,which is beneficial to the combination of electric and magnetic technologies to improve the efficiency of deep demulsification.In order to deeply explore the demulsification mechanism of W/O emulsion under the electricmagnetic synergistic field,the finite element method is used to explore the movement process of dispersed phase droplets in W/O emulsion under the action of electric,magnetic and electro-magnetic synergistic field,such as deformation and coalescence.This is an attempt to provide scientific basis for improving the technical performance of electro-magnetic demulsification.The numerical simulation model of dispersed phase droplets of W/O emulsion under AC and pulsed electric field is established.The phase field method is used to represent the oil-water distribution,and the effects of electric field and physical parameters on the deformation and coalescence of droplets are systematically studied.The results show that the larger the RMS value of electric field waveform and electric field intensity,the stronger the deformation and coalescence ability of droplets.The deforming extent of the droplet at high frequency is independent of frequency,and the frequency has little effect on coalescence rate of droplets.The ability of droplet deformation and coalescence is directly proportional to the droplet size.The droplet deformation and coalescence rate can be improved by reducing the continuous phase viscosity and oil-water interfacial tension.The effect of electric field on the deformation and coalescence of micro droplets is discussed.It is found that there is a strong linear relationship between the maximum deformation of droplets and the electric weber number under small deformation.The electric field intensity,oil phase viscosity and interfacial tension affect the coalescence efficiency of droplets by influencing the evolution of the liquid bridge between droplets.The numerical simulation model of dispersed phase droplets under the action of static magnetic field and alternating electromagnetic field is constructed,and the experiments of permanent magnetic field and electromagnetic field are carried out.The simulation and experimental results show that the magnetic field has little influence on droplet movement and the efficiency of magnetic demulsification is low.The influence of alternating magnetic field on droplet motion is greater than that of static magnetic field.Magnetic permeability is an important factor affecting the effect of magnetic demulsification.Magnetic nanoparticles(MNPs)are introduced to improve the magnetic permeability of dispersed phase droplets in emulsion.Through simulation,it is found that the movement effect of droplets is equivalent to that of the electric field.Experiments show that magnetic treatment can reduce the oil-water interfacial tension and emulsion viscosity,and indirectly promote demulsification of oil-water emulsion.From the molecular level,water molecules produce orientational polarization under the action of magnetic field,which significantly increases the probability of droplet collision and merger.A dispersed phase droplet model under the synergistic effect of vertical distribution of AC electric field and static magnetic field is established.The simulation results show that,in addition to the dipole coalescence and oscillating coalescence caused by the electric field force and dipolar force in the electric field direction,there is oscillation in the vertical electric field.And the oscillating displacement of the droplet is directly proportional to the droplet size and magnetic field intensity,and inversely proportional to the electric field frequency and continuous phase viscosity.From the molecular level,due to the coupling of the transient polarized current generated inside the droplet under the AC electric field and the magnetic field,the polarization-magnetic force perpendicular to the electric field direction is generated,which increases the oscillation coalescence in the vertical direction.Due to the ion enrichment effect,the ions enriched at the two ends of the droplet in the electric field direction are dispersed to the two ends of the droplet perpendicular to the electric field direction under the action of magnetic field,and the Coulomb repulsion force at the liquid bridge is reduced,which is beneficial to the coalescence and fusion of droplets.The demulsification effect of the synergistic effect of vertical distribution of electric and magnetic field is better than that of single electric field or single magnetic field.