| With the exploriation of oilfield,the wdiespread application of enhanced oil recovery(EOR)technology leads to the continuous increase of the water content and more intense emulsification of oil and water in oilfield produced fluid.The lower water separation efficiency of the three-phase separator leads to a longer hydraulic retention time at the successive dewatering process,a larger energy consumption for fluid heating and more dosage of demulsifier,which has significant adverse effect on the cost reduction,efficiency improvement,energy saving and emission reduction of oil-field development.In this paper,the water-in-oil(W/O)emulsion in the produced liquid was taken as the starting point,multi-scale research on electric field demulsification technology of oil-water emulsion in oil field was carried out by combining numerical simulation,laboratory experiment and field experiment.Firstly,according to the simulation results of COMSOL Multiphysics,the dynamic deformation and coalescence characteristics of dispersed water particles in W/O emulsion were studied,the effects of flow field and external electric field on the deformation and breakage of a single water drople was simulated.Then,the deformation and coalescence of two water droplets was simulated under various flow field and electric field conditions.The results showed that the optimal coalescence results for two water droplets could be obtained at electric field intensity of 3k V/cm and pulse frequency of 2000Hz.The micro-observation platform of"high-speed camera plus polarizing microscope"was set up to study the movement behavior of dispersed water droplets in W/O emulsion at various electric field parameters.The influence of electric field intensities and pulse frequencies on the deformation breakage and tensile coalescence of dispersed water particles were observed.The results showed that the optimal electric field intensity and pulse frenquency for the maximum deformation tension of a single droplet were 4 k V/cm and 2000 Hz,respectively.Experimental results verify the accurancy of the numerical simulation.Based on these results,we designed a bench scale horizontal separator with a built-in electric field,The effects of electric paratermes including electric field intensity,pulse frequency,pulse duty cycle and water content on waster demulsification were determined by,single-factor experiment.The feasibility of electric field demulsification of W/O emulsion by the combination of"high frequency/high voltage pulse AC electric field plus metal electrode"was verified,and the optimal electric parameters are voltage 5k V,pulse frequency 2k Hz and duty cycle 35%.Based on the work above a three-phase separator with a capacity of 10000m~3/d with built-in electric field enhancement was built in Gu5Joint Station of Shengli Oilfield.According to the operation performance of this facility,the field experiments were carried out,and some improvement about the electrodes were made. |
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