Emulsifier-free poly(methyl methacrylate–styrene) [P(MMA–St)] nanospheres with an average particle size of 100 nm were synthesized in an isopropyl alcohol–water medium by a solvothermal method. Then, through radical graft copolymerization of thermo-sensitive monomer N-isopropylacrylamide (NIPAm) and hydrophilic monomer acrylic acid (AA) onto the surface of P(MMA–St) nanospheres at 80 °C, a series of thermo-sensitive polymer nanospheres, named SD-SEAL with different lower critical solution temperatures (LCST), were prepared by adjusting the mole ratio of NIPAm to AA. The products were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, particle size distribution, and specific surface area analysis. The temperature-sensitive behavior was studied by light transmittance tests, while the sealing performance was investigated by pressure transmission tests with Lungmachi Formation shales. The experimental results showed that the synthesized nanoparticles are sensitive to temperature and had apparent LCST values which increased with an increase in hydrophilic monomer AA. When the temperature was higher than its LCST value, SD-SEAL played a dual role of physical plugging and chemical inhibition, slowed down pressure transmission, and reduced shale permeability remarkably. The plugged layer of shale was changed to being hydrophobic, which greatly improved the shale stability

中文翻译：

---

热敏聚合物纳米球作为页岩气钻井作业的智能堵漏剂。

通过溶剂热法在异丙醇-水介质中合成了平均粒径为100 nm的不含乳化剂的聚（甲基丙烯酸甲酯-苯乙烯）[P（MMA-St）]纳米球。然后，通过自由基接枝共聚热敏单体N-异丙基丙烯酰胺（NIPAm）和亲水性单体丙烯酸（AA）在80°C的P（MMA–St）纳米球表面上形成一系列热敏聚合物纳米球，称为SD-SEAL，具有不同的下临界溶液温度（LCST） ）通过调节NIPAm与AA的摩尔比制备。通过傅里叶变换红外光谱，透射电子显微镜，热重分析，粒度分布和比表面积分析对产物进行表征。通过光透射率试验研究了对温度敏感的行为，同时通过龙町组页岩的压力透射试验研究​​了密封性能。实验结果表明，合成的纳米粒子对温度敏感，具有明显的LCST值，其随亲水性单体AA的增加而增加。当温度高于其LCST值时，SD-SEAL起到了物理堵塞和化学抑制作用，减缓了压力传输，并显着降低了页岩渗透率。页岩的堵塞层变成疏水的，这大大提高了页岩的稳定性