特低渗砂岩油藏CO2-低界面张力黏弹流体协同驱油机理研究

目的特低渗油藏储层物性差、层间非均质性强,造成CO₂驱易发生气窜,提高采收率效果欠佳,其中,CO₂水气交替驱作为结合CO₂驱和水驱优势的方法,具有较高的适用性。为进一步改善CO₂-水交替驱的开发效果,开展了CO₂-低界面张力黏弹流体协同驱油研究。 方法通过界面张力和润湿性能测试评价低界面张力黏弹流体基本性能,并利用微观可视化驱油实验及岩心驱油实验等,探究了不同驱替方式的驱油效果和CO₂-低界面张力黏弹流体协同驱油过程中二者之间的“协同作用”机理。 结果低界面张力黏弹流体具备良好的界面活性和改变岩石表面润湿性能力,水驱后开展CO₂驱、低界面张力黏弹流体驱、CO₂-低界面张力黏弹流体交替协同驱,采收率可在水驱基础上分别提高0.91%、10.66%、16.25%,其提高采收率机理包括降低界面张力、改善流度比、改变岩石表面润湿性及乳化作用的协同效应等。 结论CO₂-低界面张力黏弹流体协同驱既可有效增强非均质特低渗砂岩油藏注CO₂过程中气体流动性控制,又能够降低CO₂萃取轻烃导致重质组分沉积的影响,具有协同增效作用。 

Study on synergistic oil displacement mechanism of CO2-low interfacial tension viscoelastic fluid alternating flooding in ultra-low permeability sandstone reservoir

ObjectiveThe low permeability reservoirs have poor physical properties and strong interlayer heterogeneity, resulting in CO₂ flooding which is prone to gas channeling, and the effect of enhancing oil recovery is not good. As a method combining the advantages of CO₂ flooding and water flooding, CO₂-water alternating flooding has high applicability. In order to further improve the development effect of CO₂-water alternating flooding, CO₂-low interfacial tension viscoelastic fluid synergistic flooding was studied. Methods The basic performance of viscoelastic fluid with low interfacial tension was evaluated by interfacial tension and wettability tests, and the oil displacement effect of different displacement methods and the "synergism" mechanism of CO₂-viscoelastic fluid with low interfacial tension in synergistic oil displacement were explored by microscopic visualization oil displacement experiment and core oil displacement experiment. ResultsViscoelastic fluid with low interfacial tension has good interfacial activity and the ability to change the wettability of rock surface. After water flooding, the recovery efficiency of CO₂ flooding, low interfacial tension viscoelastic fluid flooding and CO₂-low interfacial tension viscoelastic fluid alternating synergistic flooding increased by 0.91%, 10.66% and 16.25% respectively on the basis of water flooding. The mechanism of enhanced oil recovery includes reduction of interfacial tension, improvement of fluidity ratio, change of wettability of rock surface and synergistic effect of emulsification. ConclusionsCO₂-low interfacial tension viscoelastic fluid synergistic flooding can not only effectively enhance gas flow control during CO₂ injection in heterogeneous ultra-low permeability sandstone reservoirs, but also reduce the influence of light hydrocarbon extraction on heavy component deposition, which has synergistic synergistic effect.