Factors Affecting the Stability of Water⁃in⁃Oil Emulsions and the Liquid Accumulation Rate Model

doi:10.12422/j.issn.1672-6952.2026.01.006

Abstract

Abstract:

This study investigates the microscopic properties of water?in?oil (W/O) emulsions, focusing on their stability and the formation patterns of liquid holdup. Through emulsification experiments and microscopic observation, the effects of water content, shear rate, and carbon dioxide (CO₂) treatment on emulsion droplet size distribution and stability were systematically studied. Based on experimental data, a liquid holdup rate model was developed for the MH oil sample. The results indicate that the shear rate significantly affects the droplet size distribution and emulsion stability. A moderate shear rate (6 000~9 600 s^-1) promotes emulsion stability and yields a uniform droplet distribution. When water content is below 30%, increasing the water content reduces the droplet size; however, high water content can show phase separation. CO₂ saturation treatment can reduce interfacial tension and improve emulsion stability, but excessive CO₂ release may destabilize the oil?water interface and promote droplet coalescence. Rational control of shear rate, water content, and CO₂ concentration can effectively optimize pipeline transportation performance, reduce bottom liquid accumulation, and enhance the operational stability of the oilfield gathering and transportation system. This study provides theoretical support for the control of liquid holdup in CO₂?driven gathering pipelines and holds significant engineering application value for oilfield production management.

Key words: W/O emulsions, Shear rate, Water content, CO₂ treatment, Droplet size distribution, Liquid holdup model

摘要：

为了探讨油包水（W/O）型乳状液的微观特性及其对稳定性及积液形成规律的影响，采用搅拌乳化实验和显微观察实验，系统研究了含水率、剪切速率及CO₂过饱和处理等因素对乳状液粒径分布和稳定性的影响，并基于实验数据建立了符合MH油样的积液形成速率模型。结果表明，剪切速率显著影响乳状液的粒径分布及稳定性：中等剪切速率(6 000~9 600 s^-1)可有效增强乳状液的稳定性，并实现液滴的均匀分布；当含水率低于30%时，随着含水率的增加，液滴粒径减小，但过高的含水率可能导致分层速率下降；经CO₂饱和处理后，油水界面张力降低，乳状液的稳定性增强，但过量CO₂溢散会破坏油水界面平衡，加剧液滴聚并；合理控制剪切速率、含水率及CO₂浓度，可有效提高管道输送性能，减少底部积液，提升油田集输系统的运行稳定性。该研究成果为含CO₂驱替工艺下的集输管道积液控制提供了理论依据，对油田生产管理具有重要的工程应用价值。

关键词: W/O型乳状液, 剪切速率, 含水率, CO₂处理, 粒径分布, 积液模型

CLC Number:

TE86

Chao WU, Xuan FU, Xiaokai XING, Keshi SONG, Wenhang CHEN. Factors Affecting the Stability of Water⁃in⁃Oil Emulsions and the Liquid Accumulation Rate Model[J]. Journal of Liaoning Petrochemical University, 2026, 46(1): 45-53.

吴超, 付璇, 邢晓凯, 宋柯石, 陈文航. 油包水型乳状液稳定性影响因素及积液形成速率模型研究[J]. 辽宁石油化工大学学报, 2026, 46(1): 45-53.

Figures/Tables 13

Table 1 Physical properties and chemical composition of MH

20 ℃密度/（kg·m^-3）	凝点/℃	析蜡点/℃	w（芳香分）/%	w（胶质）/%	w（沥青质）/%
845	0.93	24.00	21.30	15.91	4.24

Fig.1 Viscosity?temperature plot of MH

Fig.2 Emulsion particle size observation device

Table 2 Shear rate of emulsion at different stirring speeds and its corresponding grades

搅拌转速/（r $⋅$ min^-1）	剪切速率/s^-1	等级
400	4 800	低剪切速率
500	6 000	中等剪切速率
600	7 200	中等剪切速率
700	8 400	中等剪切速率
800	9 600	中等剪切速率

Table 2 Shear rate of emulsion at different stirring speeds and its corresponding grades

搅拌转速/（r $⋅$ min^-1）	剪切速率/s^-1	等级
400	4 800	低剪切速率
500	6 000	中等剪切速率
600	7 200	中等剪切速率
700	8 400	中等剪切速率
800	9 600	中等剪切速率

Fig.3 Comparison of particle size frequency distributions of emulsions under different water content and stirring speed conditions

Table 3 Water separation rate of emulsion with low water content under low stirring speed

含水率/%	析水速率/（m $⋅$ s^-1)
含水率/%	400 r/min	500 r/min
10	1.37×10⁻⁶	1.08×10⁻⁶
20	1.69×10⁻⁶	1.39×10⁻⁶
30	2.64×10⁻⁶	2.23×10⁻⁶

Table 3 Water separation rate of emulsion with low water content under low stirring speed

含水率/%	析水速率/（m $⋅$ s^-1)
含水率/%	400 r/min	500 r/min
10	1.37×10⁻⁶	1.08×10⁻⁶
20	1.69×10⁻⁶	1.39×10⁻⁶
30	2.64×10⁻⁶	2.23×10⁻⁶

Fig.4 Comparison diagram of liquid accumulation of emulsions with different water contents during static storage for 0-0.5 h under low stirring speed

Fig.5 Comparison diagram of cumulative demulsification volume of emulsions with different water contents at different stirring speeds

Table 4 Water separation rate of emulsion with low water content under high stirring speed

含水率/%	析水速率/（m $⋅$ s^-1)
含水率/%	600 r/min	700 r/min	800 r/min
10	1.86×10⁻⁶	1.69×10⁻⁶	1.52×10⁻⁶
20	1.08×10⁻⁶	9.30×10⁻⁷	8.35×10⁻⁷
30	9.50×10⁻⁷	8.28×10⁻⁷	7.14×10⁻⁷

Table 4 Water separation rate of emulsion with low water content under high stirring speed

含水率/%	析水速率/（m $⋅$ s^-1)
含水率/%	600 r/min	700 r/min	800 r/min
10	1.86×10⁻⁶	1.69×10⁻⁶	1.52×10⁻⁶
20	1.08×10⁻⁶	9.30×10⁻⁷	8.35×10⁻⁷
30	9.50×10⁻⁷	8.28×10⁻⁷	7.14×10⁻⁷

Table 5 Water separation rate of emulsion with high water content at different stirring speeds

含水率/%	析水速率/（m $⋅$ s^-1)
含水率/%	400 r/min	500 r/min	600 r/min	700 r/min	800 r/min
40	1.81×10⁻⁶	2.92×10⁻⁶	4.04×10^-6	5.08×10^-6	6.02×10^-6
50	6.04×10^-7	1.22×10⁻⁶	1.94×10^-6	2.71×10^-6	3.48×10^-6

Table 5 Water separation rate of emulsion with high water content at different stirring speeds

含水率/%	析水速率/（m $⋅$ s^-1)
含水率/%	400 r/min	500 r/min	600 r/min	700 r/min	800 r/min
40	1.81×10⁻⁶	2.92×10⁻⁶	4.04×10^-6	5.08×10^-6	6.02×10^-6
50	6.04×10^-7	1.22×10⁻⁶	1.94×10^-6	2.71×10^-6	3.48×10^-6

Fig.6 Comparison diagram of effusion volume of emulsion with 40% water content at different time points

Fig.7 Comparison diagram of droplet particle size distribution and morphology before and after CO? treatment

Fig.8 Validation results of the water separation rate model under high water content

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