The application of nanoparticles for enhanced oil recovery (EOR) has been shown to be advantageous over conventional methods. Wettability alteration of reservoir rock from oil-wet to water-wet is one of the main factors in improving oil recovery from matured reservoirs. The sandstone reservoirs are generally negatively charged, and hence, a proper selection of the surface charge of nanoparticles is important. In this work, a novel nanofluid is prepared using the synergistic effect of an oppositely charged Ludox CL silica nanoparticle (positive) and an anionic Aerosol-OT (AOT) surfactant in low-salinity seawater (LSW). The positively charged Ludox CL silica nanoparticle can readily adsorb on the Berea sandstone core due to electrostatic attraction, altering the wettability. The interfacial tension (IFT) and three-phase contact angle are measured to study the effect of the nanofluid on the IFT of the crude oil–nanofluid system and the wettability of the sandstone core. At a low AOT surfactant concentration, the nanoparticles are hydrophobic because of the monolayer adsorption of AOT with a higher tendency to sit at the oil–water interface, causing a reduction in the IFT. Moreover, scanning electron microscopy and energy-dispersive X-ray analyses were used to show the adsorption of nanoparticles on the Berea core surface and the desorption of crude oil from the core. The efficiency of different imbibition fluids was evaluated via a spontaneous imbibition technique using Amott cells. Experimental results showed that the oil recovery due to spontaneous imbibition of the nanofluid conducted on the Berea core yielded the highest oil recovery rate as compared to deionized water, LSW, pure silica nanoparticles, and a pure surfactant (AOT), respectively. The nanofluid showed excellent stability, significant wettability alteration, greater reduction of IFT, and great potential as an imbibition agent for EOR applications.

中文翻译：

---

使用表面活性剂辅助功能二氧化硅纳米流体在低盐度海水中设计砂岩润湿性改变以提高采收率

已证明将纳米粒子应用于提高石油采收率 (EOR) 优于传统方法。储层岩石润湿性由亲油转变为亲水是提高成熟油藏采收率的主要因素之一。砂岩储层通常是负电荷的，因此，正确选择纳米颗粒的表面电荷很重要。在这项工作中，利用带相反电荷的 Ludox CL 二氧化硅纳米颗粒（正）和阴离子气溶胶-OT（AOT）表面活性剂在低盐度海水（LSW）中的协同作用制备了一种新型纳米流体。由于静电引力，带正电的 Ludox CL 二氧化硅纳米颗粒很容易吸附在 Berea 砂岩芯上，从而改变润湿性。测量界面张力（IFT）和三相接触角，研究纳米流体对原油-纳米流体体系的界面张力和砂岩芯润湿性的影响。在低 AOT 表面活性剂浓度下，纳米颗粒是疏水的，因为 AOT 的单层吸附具有较高的位于油水界面的倾向，导致 IFT 降低。此外，扫描电子显微镜和能量色散 X 射线分析用于显示纳米颗粒在 Berea 岩心表面的吸附以及原油从岩心的解吸。通过使用 Amott 细胞的自发自吸技术评估不同自吸流体的效率。实验结果表明，与去离子水、LSW、纯二氧化硅纳米粒子和纯表面活性剂 (AOT) 相比，在 Berea 岩心上进行的纳米流体自发吸收导致的采油率最高。纳米流体表现出优异的稳定性、显着的润湿性改变、更大的 IFT 降低以及作为 EOR 应用的自吸剂的巨大潜力。