Recently, nanoparticles have proven to enhance oil recovery on the core-flood scale in challenging high-pressure high-temperature reservoirs. Nanomaterials generally appear to improve oil production through wettability alteration and reduction in interfacial tension between oil and water phases. Besides, they are environmentally friendly and cost-effective enhanced oil recovery techniques. Studying the rheological properties of nanoparticles is critical for field applications. The instability of nanoparticle dispersion due to aggregation is considered as an unfavorable phenomenon in nanofluid flooding while conducting an EOR process. In this study, wettability behavior and rheological properties of surface-treated silica nanoparticles using internal olefins sulfonates (IOS_20–24 and IOS_19–23), anionic surfactants were investigated. Surface modification effect on the stability of the colloidal solution in porous media and oil recovery was inspected. The rheology of pure and surface-treated silica nanoparticles was investigated using a HPHT rheometer. Morphology and particle size distributions of pure and coated silica nanoparticles were studied using a field emission scanning electron microscope. A series of core-flood runs was conducted to evaluate the oil recovery factor. The coated silica nanoparticles were found to alter rheological properties and exhibited a shear-thinning behavior as the stability of the coated silica nanoparticles could be improved considerably. At low shear rates, the viscosity slightly increases, and the opposite happens at higher shear rates. Furthermore, the surface-modified silica nanoparticles were found to alter the wettability of the aqueous phase into strongly water-wet by changing the contact angle from 80° to 3° measured against glass slides representing sandstone rocks. Oil–water IFT results showed that the surface treatment by surfactant lowered the oil–water IFT by 30%. Also, the viscosity of brine increased from 0.001 to 0.008 Pa s by introducing SiO₂ nanoparticles to the aqueous phase for better displacement efficiency during chemical-assisted EOR. The core-flood experiments revealed that the ultimate oil recovery is increased by approximately 13% with a surfactant-coated silica nanofluid flood after the conventional waterflooding that proves the potential of smart nanofluids for enhancing oil recovery. The experimental results imply that the use of surfactant-coated nanoparticles in tertiary oil recovery could facilitate the displacement efficiency, alter the wettability toward more water-wet and avoid viscous fingering for stable flood front and additional oil recovery.

中文翻译：

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使用内部烯烃磺酸盐评估表面改性的二氧化硅纳米颗粒增强采油率的潜力

最近，在具有挑战性的高压高温油藏中，纳米粒子已被证明可以提高岩心驱油规模的采收率。纳米材料通常似乎通过改变润湿性和减少油相与水相之间的界面张力来提高产油量。此外，它们是环保且具有成本效益的增强采油技术。研究纳米颗粒的流变特性对现场应用至关重要。由于聚集引起的纳米颗粒分散体的不稳定性被认为是在进行EOR过程时纳米流体驱替中的不利现象。在这项研究中，使用内部烯烃磺酸盐的表面处理二氧化硅纳米颗粒的润湿性和流变特性（IOS _20-24和IOS _19-23），研究了阴离子表面活性剂。检查了表面改性对胶体溶液在多孔介质中的稳定性和采油率的影响。使用HPHT流变仪研究了纯的和经表面处理的二氧化硅纳米颗粒的流变性。使用场发射扫描电子显微镜研究了纯的和包覆的二氧化硅纳米粒子的形貌和粒径分布。进行了一系列的核心驱油作业，以评估采油率。发现涂覆的二氧化硅纳米颗粒改变了流变性质并表现出剪切稀化行为，因为涂覆的二氧化硅纳米颗粒的稳定性可以大大提高。在低剪切速率下，粘度略有增加，而在较高剪切速率下则相反。此外，通过将与代表砂岩岩石的载玻片测得的接触角从80°改变为3°，发现表面改性的二氧化硅纳米颗粒将水相的润湿性改变为强水润湿性。油水IFT结果表明，表面活性剂的表面处理使油水IFT降低了30％。此外，通过引入SiO，盐水的粘度从0.001 Pa升至0.008 Pa s在化学辅助EOR过程中，将_2种纳米颗粒添加到水相中以提高置换效率。岩心驱油实验表明，在常规注水后，表面活性剂涂覆的二氧化硅纳米流体驱油的最终采收率提高了约13％，这证明了智能纳米流体具有提高采油率的潜力。实验结果表明，在三次采油中使用表面活性剂包覆的纳米颗粒可以提高驱油效率，改变向更多水润湿的润湿性，避免粘性指法获得稳定的洪水前锋和额外的采油率。