Hadia Nanji J, Ng Yeap Hung, Stubbs Ludger Paul, Torsæter Ole
Institute of Chemical and Engineering Sciences, Agency for Science, Technology, and Research (A*STAR), 1 Pesek Road, Jurong Island, Singapore 627833, Singapore.
Department of Geoscience and Petroleum, Norwegian University of Science and Technology (NTNU), 7031 Trondheim, Norway.
Nanomaterials (Basel). 2021 Mar 11;11(3):707. doi: 10.3390/nano11030707.
The stability of nanoparticles at reservoir conditions is a key for a successful application of nanofluids for any oilfield operations, e.g., enhanced oil recovery (EOR). It has, however, remained a challenge to stabilize nanoparticles under high salinity and high temperature conditions for longer duration (at least months). In this work, we report surface modification of commercial silica nanoparticles by combination of zwitterionic and hydrophilic silanes to improve its stability under high salinity and high temperature conditions. To evaluate thermal stability, static and accelerated stability analyses methods were employed to predict the long-term thermal stability of the nanoparticles in pH range of 4-7. The contact angle measurements were performed on aged sandstone and carbonate rock surfaces to evaluate the ability of the nanoparticles to alter the wettability of the rock surfaces. The results of static stability analysis showed excellent thermal stability in 3.5% NaCl brine and synthetic seawater (SSW) at 60 °C for 1 month. The accelerated stability analysis predicted that the modified nanoparticles could remain stable for at least 6 months. The results of contact angle measurements on neutral-wet Berea, Bentheimer, and Austin Chalk showed that the modified nanoparticles were able to adsorb on these rock surfaces and altered wettability to water-wet. A larger change in contact angle for carbonate surface than in sandstone surface showed that these particles could be more effective in carbonate reservoirs or reservoirs with high carbonate content and help improve oil recovery.
纳米颗粒在油藏条件下的稳定性是纳米流体成功应用于任何油田作业（如提高采收率，EOR）的关键。然而，在高盐度和高温条件下使纳米颗粒长时间（至少数月）保持稳定仍然是一个挑战。在这项工作中，我们报道了通过两性离子硅烷和亲水性硅烷相结合对商用二氧化硅纳米颗粒进行表面改性，以提高其在高盐度和高温条件下的稳定性。为了评估热稳定性，采用静态和加速稳定性分析方法来预测纳米颗粒在pH值为4 - 7范围内的长期热稳定性。在老化的砂岩和碳酸盐岩表面进行接触角测量，以评估纳米颗粒改变岩石表面润湿性的能力。静态稳定性分析结果表明，改性纳米颗粒在60℃的3.5% NaCl盐水和合成海水中放置1个月具有优异的热稳定性。加速稳定性分析预测改性纳米颗粒可以保持稳定至少6个月。在中性润湿性的贝雷砂岩、本特海默砂岩和奥斯汀白垩岩上进行的接触角测量结果表明，改性纳米颗粒能够吸附在这些岩石表面并将润湿性改变为水湿。碳酸盐表面的接触角变化比砂岩表面大，表明这些颗粒在碳酸盐油藏或碳酸盐含量高的油藏中可能更有效，并有助于提高采收率。
