Abstract:

Demulsification of emulsion is a difficult technical problem to be solved in the process of oilfield production in high water cut period. Electric field demulsification is an effective ways to solve this problem because of its advantages of clean and high efficiency. In this paper, numerical simulation and experimental verification were applied to study the coalescence and separation characteristics of double droplets induced by the step and ramp signal electric field in the process of electric dehydration. The results show that under the action of ramp signal electric field, the pumping suction effect caused by interfacial tension is far greater than the necking effect caused by electric field, which is conducive to the coalescence of droplets, and reduces the probability of secondary emulsification of droplets. While applying the step signal electric field, the demulsification of the droplet can be achieved within a certain range, but the droplet is prone to secondary emulsification during coalescence. From the perspective of the effect of electric field on the continuous phase, it is found that the step signal electric field not only drives the droplet deformation and coalescence, but also has an obvious effect on the continuous phase. The step signal electric field increases the turbulence effect in the continuous phase, which is unfavorable to the electric dehydration process. Therefore, applying ramp signal to induce droplet coalescence could reduce the probability of secondary emulsification in the electric dehydration process.

Key words: droplet, phase field method, electric dehydration, coalescence, separation, numerical simulation

摘要：

乳状液破乳分离是目前高含水期油田开采过程中难以解决的技术问题，电场破乳方法具有高效清洁等优点，是解决该问题的有效手段。采用数值模拟与试验验证相结合的方法研究电脱水过程中阶跃、斜坡电场诱导下双液滴的聚合与分离特性。结果表明，在斜坡电场作用下，界面张力引起的泵吸作用大于电场力引起的颈缩作用，有利于液滴聚并，且液滴发生二次乳化现象的概率降低。而施加阶跃电场时，一定范围内能够达到液滴破乳的目的，但液滴在聚并过程中易发生二次乳化现象。从电场对连续相影响的角度分析发现，阶跃电场不仅对液滴具有驱动作用，对连续相的影响也较为明显，阶跃电场会增大连续相内湍流作用，不利于电脱水过程。因此，采用斜坡信号诱导液滴聚合能够降低二次乳化现象发生的概率。

关键词: 液滴, 相场方法, 电脱水, 聚结, 分离, 数值模拟