纳米SiO_(2)流体的性能及其渗吸驱油效果评价

Performance and Imbibition Oil Displacement Effect Evaluation of Nano-silica Fluid

在分析储层岩石物性及地层水离子成分的基础上,通过实验评价了0.5%纳米SiO_(2)、0.5%纳米SiO_(2)+0.3%十二烷基硫酸钠表面活性剂、地层水的流变性、界面张力和接触角等参数,进而考察这3种不同组分流体的渗吸驱油效果。结果表明:实验所用纳米SiO_(2)流体中纳米颗粒的粒径介于10~100 nm,其中介于25~60 nm的占比最高,达75%以上,粒径均值约40 nm。这种纳米SO_(2)流体具有胀塑性流体特征,其与原油的界面张力为12.05 mN/m,约为地层水与原油界面张力的30%,能够将亲油性的岩心改变为弱亲水性,接触角从126°减小为86°;这种纳米SiO_(2)流体的渗吸驱油效率约为44.67%,比地层水的渗吸驱油效率提高了13.59%。纳米SiO_(2)颗粒和加入十二烷基硫酸钠可不同程度降低流体与原油的界面张力,改变岩石孔喉表面的润湿性,促进岩心中的油水置换,最终提高渗吸采收率。

On the basis of analyzing the physical properties of reservoir rocks and the ion composition of formation water,the rheological properties,interfacial tension and contact angle of 0.5% nano SiO_(2),0.5% nano SiO_(2)+0.3% sodium dodecyl sulfate surfactant solution and formation water were evaluated through experiments,and the imbibition oil displacement effect of three different component fluids was investigated.The results indicate that the size of nanoparticles in the nano SiO_(2) fluid is approximately 40 nm.Nano SO_(2) fluid has the characteristics of swelling plastic fluid,and its interfacial tension with crude oil is 12.05 mN/m,which is about 30% of the interfacial tension between formation water and crude oil.Nano SO_(2) fluid can change the lipophilic rock core to weakly hydrophilic rock core,reducing the contact angle from 126° to 86°.The oil displacement efficiency of nano SiO_(2) fluid is about 44.67%,which is 13.59% higher than that of formation water.Silicon dioxide nanoparticles and sodium dodecyl sulfate can reduce the interfacial tension of fluid and crude oil to varying degrees,change the wettability of the rock pore throat surface,promote oil-water displacement in the rock,and ultimately improve the imbibition oil displacement efficiency.