Abstract: Electrodehydration is an efficient method to solve the difficult crude oil production fluid dehydration problem. Droplet deformation, droplet coalescence, droplet sedimentation and droplet-interface coalescence commonly occur during crude oil electrodehydration. The electric field parameters and physical property parameters have a significant influence on the droplet coalescence efficiency. The droplet-interface electrocoalescence process was investigated using COMSOL Multiphysics software. According to the field conditions of oilfield, the droplet-interface dynamic evolution behaviors were studied by changing the electric field parameters (electric field strength and electric field waveform) and physical property parameters (surface tension, electric conductivity, continuous phase viscosity, droplet size droplet-interface distance). The results showed that the droplet-interface partial coalescence degree increased with increasing electric field strength, droplet size and droplet-interface distance and the droplet-interface complete coalescence occurred at CaE≤5.61, D<0.69D0. The droplet-interface partial coalescence degree decreased with increasing surface tension and continuous phase viscosity, and the droplet-interface complete coalescence occurred at γ*>4.0 and Oh≥0.076. Compared with the DC field, pulsed field with different waveforms can effectively promote droplet-interface coalescence. When σ*≤1.0, with increasing electrical conductivity, the droplet dipole moment increased, and the surface charge movement and transfer speed increased, the dimensionless secondary droplet volume (Vr) increased significantly; When σ*>1.0, the change of droplet dipole moment is small and stable, and Vr gradually decreased, thus the droplet-interface partial coalescence degree first increased and then decreased. The research results provide a theoretical basis and research basis for the design and development of efficient and compact electrodehydration equipment, which has important academic significance and broad application prospect for energy saving, carbon reduction and green low-carbon transformation of oilfield.

Key words: electrocoalescence, oil-water interface, level set method, numerical simulation, electrohydrodynamics

摘要： 电脱水是解决原油采出液脱水难题的高效技术手段。本工作围绕液滴-界面电聚并过程，采用COMSOL Multiphysics软件开展数值模拟，针对油田现场工况，系统分析了电场参数(电场强度和电场波形)与物性参数(界面张力、电导率、连续相黏度、液滴粒径、液滴-界面距离)对液滴-界面动力学演化行为的影响规律。结果表明，随电场强度、液滴粒径和液滴-界面距离的增加，液滴-界面部分聚并程度增加；当电毛细管数CaE≤5.61、液滴直径D<0.69D0时，液滴-界面发生完全聚并。随界面张力、连续相黏度的增加，液滴-界面部分聚并程度减弱，当界面张力γ*>4.0、连续相黏度Oh≥0.076时，液滴-界面完全聚并。相比于直流电场，脉冲电场能有效促进液滴-界面完全聚并。随电导率的增加，无量纲二次液滴体积(Vr)先增大后减小。本研究结果为开发高效紧凑的电脱水设备提供了理论依据，对油田节能降碳及绿色低碳转型具有重要意义。

关键词: 静电聚并, 油水界面, 水平集方法, 数值模拟, 电流体动力学