无碱二元体系的黏弹性和界面张力对水驱残余油的作用

三元复合驱含碱驱油体系会大幅度降低聚合物溶液的黏弹性,引起地层粘土分散和运移、形成碱垢及导致地层渗透率下降。为此提出利用不加碱可形成超低界面张力的聚合物/甜菜碱表面活性剂二元复合体系驱油。通过流变性实验及微观模型驱油实验,分析了表面活性剂对聚合物表面活性剂二元复合体系黏弹性的影响和聚合物表面活性剂二元复合体系的黏弹性及界面张力对采收率的影响。对聚合物表面活性剂二元复合体系提高水驱后残余油采收率机理的研究表明:在驱替水驱后残余油过程中,聚合物表面活性剂二元复合体系利用了聚合物溶液的黏弹特性和表面活性剂的超低张力界面特性,水驱后残余油以油丝和乳状液形式被携带和运移,随着二元驱油体系的黏弹性的增加和界面张力的降低,水驱后二元驱后的采收率增加,降低界面张力的驱油效果(指达到超低)比提高体系的黏弹性的效果更明显。

Influence of viscoelasticity and interfacial tension of non-alkali binary compound solution on recovery efficiency of residual oil after water flooding

The alkali in the alkali surfactant polymer (ASP) flooding system could reduce the viscoelasticity of the polymer solution, which results in the dispersion and migration of clay and the scaling of alkali in the formation and reduction of reservoir permeability. A new surfactant polymer binary compound system (SP) without alkali was proposed and used to attain ultra low interfacial tension of oil. The influence of surfactant on the viscoelasticity of surfactant polymer compound system was analyzed by rheology experiment and the microscopic oil displacement experiment. The effects of viscoelasticity and interfacial tension of SP compound system on recovery efficiency were discussed. The mechanism for enhancing the recovery efficiency of residual oil in SP compound system after water flooding indicated that the mobility control of polymer and the ultra low interfacial tension of the surfactant could be fully utilized and the residual oil after water flooding was carried out and migrated in the form of “oil thread” and emulsion drops during the displacement of residual oil after water flooding. The recovery efficiency of SP flooding after water flooding increased with the increase of viscoelasticity and the decrease of interfacial tension. Oil displacement effect of reducing interfacial tension (aiming to the ultralow interfacial tension) was more obvious than that of enhancing viscoelasticity of SP compound system.