粗油水乳状液的流变特性

Rheological properties of coarse oil-water emulsions

粗油水乳状液相对于稳定的油水乳状液而言,其静置会出现两相分离的现象,类似于两相管流的分散程度。针对现有乳状液表观黏度理论不适用于粗油水乳状液的问题,采用Haake RS 6000流变仪对不同含油率下粗乳状液的流变曲线进行测量,同时观察温度变化对粗乳状液黏度的影响。研究结果表明:粗乳状液因含油率不同而表现出不同类型的非牛顿流体特征,水为连续相时表现为膨胀性流体,油为连续相时表现为假塑性流体。乳状液的黏度随含油率升高逐渐增加,并在60%含油率处达到最大值,当含油率继续升高时,随着含油率升高,其黏度逐渐减小至纯油的黏度值。在不同温度下,相同含油率的乳状液黏度随着温度升高呈指数规律降低。此外,根据实验数据对已有的油水乳状液黏度计算模型进行评估,并对应用于低含油率粗乳状液的黏度模型进行修正,提高了预测精度。对粗油水乳状液流变性的研究成果,将进一步提高原油开采及运输中管道压降预测的精度,为管道运输系统的精确设计提供可靠的物性参数。(图9,表3,参20)

Compared with stabilized oil-water emulsion, coarse oil-water emulsion tends to separate into two phases after setting aside, similar to the dispersion of two-phase flow. The existing superficial viscosity theory for emulsion is not suitable for coarse crude oil-water emulsion. In this paper, Haake RS6000 rheometer is used to measure flow curves at different oil content of coarse oil-water emulsion, and the effect of temperature on the coarse oil-water emulsion viscosity is observed at the same time. The results show that coarse oil-water emulsion shows different types of non-Newtonian fluid characteristics at different oil content. When water is the continuous phase, the emulsion shows the features of expansion fluid, when crude oil is the continuous phase, the emulsion shows features of pseudoplastic fluid. The emulsion viscosity increases gradually with the increase of oil content and reaches the maximum at 60% oil content. As oil content continues to raise, the viscosity start to decrease to pure oil＇s level. At different temperatures, the viscosity of the emulsion of the same oil content decreases exponentially as the temperature increases. In addition, based on the experimental data, the existing oil-water emulsion viscosity calculation model is evaluated, and the viscosity model for coarse oil-water emulsion with low oil content is corrected, resulting in improvement in its prediction accuracy. The study results of rheological properties of coarse oil-water emulsion will enhance the prediction accuracy of pressure drop in the pipeline of crude oil exploitation and transportation, and provide a reliable physical parameters to the design of pipeline transportation system.