页岩地层纳米级微孔、微裂缝发育，常规封堵剂粒径较大，难以封堵页岩内孔缝。以无机纳米二氧化硅为 核，以聚（苯乙烯-丙烯酸丁酯-丙烯酸）为壳（单体质量比为10∶2∶1），基于乳液聚合法制备了耐高温核壳型纳米 封堵剂（CLG-NM）。通过红外光谱、透射电镜、动态光散射、热重实验对封堵剂进行了表征，通过页岩压力传递 实验评价了其封堵性能。结果表明，CLG-NM粒径分布为40～300 nm，中值粒径为89.4 nm，在372 ℃以下的热 稳定性良好。CLG-NM与现场油基钻井液的配伍性良好，3% CLG-NM对油基钻井液流变性的影响较小，高温 高压滤失量（180 ℃老化 16 h）从 3.1 mL 降至 2.8 mL，破乳电压高于 700 mV。CLG-NM 可进入页岩内的纳米 孔-缝进行封堵，在现场油基钻井液中加入CLG-NM的上游压力穿透岩心的时间为19.5 h，封堵效果好于国内外 同类产品。
Nano pores and micro fractures are well developed in shale formation. However，the particle size of conventional plugging agent is large and it is difficult to plug pores and fractures in shale. A core-shell nano plugging agent（CLG-NM）with high temperature resistance was prepared by using inorganic nano silica as the core and poly（styrene-butyl acrylate-acrylic acid）as the shell in mass ratio 10∶2∶1 through emulsion polymerization method. The plugging agent was characterized by infrared spectroscopy， transmission electron microscopy，dynamic light scattering and thermogravimetry，and its plugging performance was evaluated by shale pressure transferring experiment. The results showed that the particle size distribution of CLG-NM was 40—300 nm，and the median particle size was 89.4 nm. CLG-NM maintained good thermal stability below 372 ℃. Furthermore，CLG-NM had good compatibility with oil-based drilling fluid. 3% CLG-NM had little effect on the fluidity of oil-based drilling fluid. The high temperature and high pressure filtration decreased from 3.1 mL to 2.8 mL after aging at 180 ℃ for 16 h，and the demulsification voltage kept higher than 700 mV. CLG-NM could enter the nano pores and fractures in the shale for plugging. The upstream pressure of oil-based drilling fluid contained CLG-NM could penetrate the core for 19.5 h. Compared with similar products at home and abroad，CLG-NM had better plugging effect on nano pores and fractures in shale.