The phase behavior of microemulsion systems formed by supercritical carbon dioxide, water, surfac-tant, and ethanol were investigated utilizing the phase equilibrium apparatus. The cloud-point pressures and densi-ties of the microemulsion systems were measured. The influences of the concentrations of water and surfactant, sur-factant types, and the mixed surfactants were evaluated. The cloud-point pressures increased with the rising of the concentrations of water and surfactant. The densities increase with the rising of the cloud-point pressures. For the single surfactant, AES-2 and AEC-3 showed the lowest cloud-point pressure up to 13. 8 MPa and 13. 1 MPa, re-spectively, which is higher than AOT which up to 10. 8 MPa. For the mixed surfactants, AEC-3/ AOT showed the lowest cloud-point pressure up to 8. 60 MPa and the density up to 0. 58 g·cm-3 when the mass ratio was 1∶1. This study is the base research and can provide fundamental data for the application of the supercritical carbon dioxide microemulsion in enhanced heavy oil recovery.%利用超临界二氧化碳相行为评价装置,研究了超临界二氧化碳/水/表面活性剂/乙醇微乳液体系的相行为,考察了表面活性剂的结构、表面活性剂的含量、水的含量、体系的温度和表面活性剂的复配对微乳液体系浊点压力和密度的影响。结果表明：微乳液体系的浊点压力分别随着水含量的增加,表面活性剂含量的增加和温度的升高而增加；体系的浊点压力越高,密度越大。不同结构的表面活性剂中,AES-2和AEC-3的浊点压力最低分别能达到13.8和13.1 MPa,要高于AOT的10.8 MPa。但将表面活性剂AEC-3和AOT按质量比1∶1复配时体系的浊点压力最低可达到8.6 MPa,密度为0.58 g·cm－3。研究可为超临界二氧化碳微乳液在提高稠油采收率方面的应用提供基础数据。
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