高含水后期乳状液的驱油效果与作用机理分析

Research on Profile Control and Displacement Mechanism of Discontinuous Emulsion in Late High Water-cut Stage

为了揭示乳状液在多孔介质中的驱油作用与提高波及体积的机理,根据大庆油田主力区块地质特征和地层流体特性,选用甜菜碱型表面活性剂和非离子表面活性剂混合体系,利用岩心乳化方法模拟地下乳化过程,采用三管并联岩心驱替实验研究不同渗透率极差条件下乳状液的驱油效果和各层产液变化,通过与同界面张力的表面活性剂驱的驱油效果和各层产液的对比,从乳状液驱相渗曲线和贾敏效应两个方面分析乳状液调驱的机理。研究结果表明,岩心渗透率变异系数越大,乳状液驱阶段原油采出程度越高、高渗透层产液下降幅度越大。对于平均渗透率400×10^(-3)μm^2、渗透率变异系数为0.72的三层非均质岩心,乳状液驱能够比水驱提高采收率16.98%,中低渗透层提高产液16%。乳状液在驱替过程中由于贾敏效应能够形成较好的封堵作用,可改变水相的相渗曲线,具有较好的流度控制作用,可避免表面活性剂驱过程中驱替液沿高渗透油层窜流的现象。高含水后期乳状液驱能够扩大波及体积的主要原因是乳状液的黏弹性引起水相相对渗透率的改变和大粒径乳状液的贾敏效应,驱油效果优于表面活性剂驱。

In order to discover the oil displacing action and the enlarged swept volume mechanism of emulsion in porous medium,the mixed system of betaine surfactant and nonionic surfactant was used to conduct experiments based on the geological features and fluid characteristics of major blocks in Daqing oilfied. The oil displacing action of the emulsion and the produced fluid proportion in layers with different permeability was studied on triple parallel heterogeneous cores with different permeability variation coefficient using core emulsification way to simulate the underground emulsification process,and the emulsion flooding mechanism was probed from the aspects of relative permeability curve and Jamin effect of the emulsion flooding by comparing with that of the surfactant flooding with the same interfacial ability. The result showed that the greater permeability variation coefficient,the greater the oil recovery degree of the emulsion flooding,the greater the reduction of the produced fluid capacity in high permeability layers.As for the heterogeneous cores of three layers with even permeability of 400 × 10^（-3）μm2and permeability variation coefficient of0.72,the oil recovery of emulsion flooding was more than that of water flooding by 16.98% and fluid production in middle-low permeability layers was more by 16%. The emulsion could play a better plugging role in the displacing process due to the jamin effect,and the relative permeability curve of the water phasev was changed,as a result,the emulsion had good controlling fluid action,which could avoid the channeling phenomenon which happened in surfactant flooding.The emulsion was able to enlarge the swept volume in late high water cut stage,which was mainly due to the change of water phase relative permeability raised by the viscoelasticity of emulsion and Jamin effect of emulsion of large particle size. The oil displacing effect of the emulsion flooding was better than that of the surfactant flooding.