超临界CO2处理对乳状液稳定性的影响机理研究

摘要

超临界CO2(scCO2)混相驱在提高原油采收率的同时,也显著改变采出原油乳液的性质.利用自主研发的CO2-原油混相装置在模拟地层条件下对长庆原油进行混相处理,分别使用流变仪、电导率仪和显微镜研究了混相处理前后长庆原油及其W/O乳液的流变性、稳定性和微观形貌.实验结果表明,scCO2处理改变了长庆原油的组成,破坏了沥青质溶剂化层结构,使得失去保护的沥青质胶粒更易吸附于油水界面;scCO2处理也使得析出的蜡晶尺寸更加细小,数量增加,这将导致乳液黏度显著增大.上述变化导致scCO2处理后W/O原油乳液的水滴粒径变小、分布更加均匀,宏观表现为乳液体系的流动性恶化、稳定性增强.%The supercritical carbon dioxide (scCO2) miscible flooding improves oil recovery while significantly improving the properties of crude oil emulsion.Research was conducted with a self-developed high-pressure CO2-crude mixing container.The contact process of scCO2 and crude oil in miscible flooding was simulated under formation condition.After scCO2 mixing process, the viscosity, stability and microscopic morphology of crude oil and emulsion were studied by rheological measurement, conductivity meter and microscopic observation.The experimental results show that, the composition of Changqing crude oil changes after scCO2 miscible flooding, the asphaltene solvation layer structure is destroyed, which helps the asphaltene particles to be more easily adsorbed on the oil-water interface.The size of wax crystals becomes smaller, the number of them increases, and the emulsion viscosity increases significantly.All of those changes lead to the deterioration of liquidity and enhancement of emulsion stability.