Nanoemulsions consist of small particle size, uniform dispersion, and long-term stability, making them suitable for use in enhanced oil recovery for low-permeability reservoirs. In this paper, an ultrastable oil-in-water nanoemulsion was prepared using the emulsification inverse phase method at a constant temperature. Rheology, multiple-light scattering, laser particle size analyzer, and optical microscope were used to determine the effects of the emulsifier and water content, salinity, and reservoir temperature on the stability of the prepared nanoemulsion. The oil washing performance of nanoemulsion was tested by the weight-loss method. Results show that the nanoemulsions tend to be stable with an increase in the emulsifier content (≥8 wt. %). As the water content increases, the viscosity of nanoemulsions gradually decreases as well as its elasticity. The salinity and temperature are found to have minor effects on the stability of nanoemulsions. At the same time, the oil washing efficiency of nanoemulsion can reach as high as 83%. Hence, this study will provide theoretical supports and guidelines for the preparation of highly efficient nanoemulsion flooding systems for low-permeability reservoirs.

中文翻译：

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水包油（O/W）纳米乳液的稳定性及其洗油性能提高采收率

纳米乳液具有粒径小、分散均匀和长期稳定性等特点，适用于低渗透油藏的提高采收率。本文采用乳化反相法在恒温条件下制备了一种超稳定的水包油纳米乳。采用流变学、多光散射、激光粒度分析仪和光学显微镜测定乳化剂和含水量、盐度和储层温度对制备的纳米乳稳定性的影响。采用失重法测试纳​​米乳的洗油性能。结果表明纳米乳液随着乳化剂含量的增加（≥8wt.%）趋于稳定。随着含水量的增加，纳米乳的粘度逐渐降低，弹性也逐渐降低。发现盐度和温度对纳米乳液的稳定性影响较小。同时，纳米乳液的洗油效率可高达83%。因此，本研究将为低渗透油藏高效纳米乳液驱油体系的制备提供理论支持和指导。