含蜡原油及其乳状液体系微观结构观测的新方法

doi:10.16085/j.issn.1000-6613.2022-1821

摘要/Abstract

摘要：

基于流变-原位显微同步测量技术和改进的复合型光源，构建了对含蜡原油及其乳状液体系微观结构观测的新方法。实际观测结果表明：新构建的显微观测方法观测到的蜡晶数量比偏光显微镜观测到的蜡晶数量高出70%，并且在识别微小尺寸蜡晶方面具有更高精度，与常规偏光显微观测结果相比，识别出的1~3μm范围内的蜡晶数量要多150%，刻画的1~2μm范围内蜡晶分形维数要高15%，使得新构建的显微观测方法对恶化初始冷却温度下形成的致密型蜡晶具有更为突出的观测优势。此外，新观测方法识别出的恶化和较优初冷温度下的蜡晶边缘间距差值更大，约是常规显微观测结果的2倍，更能体现出不同初冷温度下的蜡晶结构差异，与原油流变性的关联性也更显著。动态剪切条件下的蜡晶微观形貌受流场影响显著，随剪切速率增大，蜡晶形态和排列与流场的协同性增强。相比于离线观测，原位显微观测获得的蜡晶微观形貌与原油流变性的关联性更显著，更有利于从微观尺度阐释含蜡原油的流变性机制。新观测方法可以实现对原油乳状液中蜡晶和乳化水滴的同时观测，在识别两者相互作用和形成聚集结构方面具有更好的识别质量。

关键词: 流变学, 含蜡原油, 乳液, 流变-显微同步测量技术, 显微结构, 恶化初冷温度, 剪切速率

Abstract:

Based on the rheological-in-situ microscopic synchronous measurement technique and the improved composite light source, a new method for observing the microstructure of waxy crude oil and its emulsion system was established. The actual observation results showed that the number of wax crystals observed by the newly constructed microscopic observation method was 70% higher than that observed by polarizing microscope, and had higher accuracy in identifying small size wax crystals compared with conventional polarizing microscopic observation results. The number of wax crystals in the range of 1—3μm was 150% more, and the fractal dimension of wax crystals in the range of 1—2μm was 15% higher. The newly constructed microscopic observation method had a more prominent observation advantage for the dense wax crystals formed under the deterioration of the initial cooling temperature. In addition, the deterioration identified by the new observation method and the difference between the edge spacing of wax crystals at the optimal initial cooling temperature were larger, which was about twice that of the conventional microscopic observation results. It can better reflect the wax crystal structure at different initial cooling temperatures. The correlation with crude oil rheology was also more significant. The microscopic morphology of wax crystals under dynamic shearing conditions was significantly affected by the flow field. With the increase of shear rate, the synergy between the morphology and arrangement of wax crystals and the flow field increased. Compared with offline observation, the correlation between the wax crystal micromorphology and crude oil rheology obtained by in-situ microscopic observation was more significant, which was more beneficial to explain the rheological mechanism of waxy crude oil from the microscopic scale. The new observation method can realize the simultaneous observation of wax crystals and emulsified water droplets in crude oil emulsion, and had better identification quality in identifying their interaction and aggregation structures.

Key words: rheology, waxy crude oil, emulsion, rheological-microscopic synchronous measurement technique, microstructure, deteriorating initial cooling temperature, shear rate

中图分类号:

TE832

赵健, 卓泽文, 董航, 高文健. 含蜡原油及其乳状液体系微观结构观测的新方法[J]. 化工进展, 2023, 42(8): 4372-4384.

ZHAO Jian, ZHUO Zewen, DONG Hang, GAO Wenjian. A new method for observation of microstructure of waxy crude oil and its emulsion system[J]. Chemical Industry and Engineering Progress, 2023, 42(8): 4372-4384.

图/表 17

表1 3种原油基本物性

性质	数值
性质	呼伦贝尔原油	大庆原油	塔木察格原油
20℃时密度/kg·m^-3	832.6	855.4	877.3
析蜡点/℃	47.0	53.5	55.5
凝点/℃	18.0	29.0	31.0
饱和烃质量分数/%	65.8	68.9	63.0
芳香烃质量分数/%	18.0	19.1	14.85
胶质质量分数/%	11.8	8.8	18.0
沥青质质量分数/%	4.4	3.2	4.15

图1 实验装置

表2 不同实验油样的恶化和较优初冷温度

油样	恶化初冷温度/℃	较优初冷温度/℃
呼伦贝尔原油	60	70
大庆原油	70	80
塔木察格原油	70	80

图2 流变-显微同步测量技术获得的恶化初冷温度下结果

图3 常规偏光显微镜获得的恶化初冷温度下结果

图4 两种观测方法下蜡晶数量及粒径分布的对比

图5 呼伦贝尔原油两种观测方法下1~2μm蜡晶的分形维数

图6 在较优初冷温度下呼伦贝尔原油在降温过程中蜡晶显微序列图像

图7 较优初冷温度时两种观测方法下蜡晶数量及粒径分布的对比

图8 恶化初冷温度下结果

图9 较优初冷温度下结果

图10 恶化和较优初冷温度下的蜡晶边缘距差值随观测温度的变化

图11 不同剪切速率下呼伦贝尔原油中原位蜡晶显微图像（图中红色箭头为流场方向）

图12 突降至0.5s-1剪切速率时的显微图像（图中红色箭头为流场方向）

图13 动态剪切下和剪切突降至0.5s-1时蜡晶微观参数和黏度的变化

表3 不同温度下蜡晶微观特征参数与原油流变性的灰色关联度

项目	温度/℃	数量	与流场方向夹角/(°)	分形维数
剪切过程中	40	0.5492	0.7143	0.6725
剪切过程中	30	0.8316	0.6835	0.5838
剪切速率突降后	40	0.5328	0.7036	0.6674
剪切速率突降后	30	0.7274	0.6218	0.5406

图14 不同实验仪器对20%含水率的W/O型含蜡原油乳状液观测结果对比

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