乳液聚合法合成钻井液用纳米级封堵剂研究

Study on synthesis of nanoscale plugging agent for drilling fluid by emulsion polymerization

以苯乙烯、丁二烯为共聚单体,2-甲基-2-丙烯酸-2-羟乙基酯磷酸酯(HEMAP)为偶联剂,采用乳液聚合法在气相纳米二氧化硅表面接枝聚合物壳层,合成了纳米级封堵剂NPS。通过核磁共振、热失重、透射电镜、激光粒度分析等方法表征聚合产物,表征分析证明单体发生有效聚合,反应生成形状较规则柔性微球,乳液粒径中值93nm,除桥堵作用外,微球表面的亲水基团也会与地层黏土矿物产生多点吸附,使封堵层更加致密,纳米乳液抗温性较好,这是因为分子结构中引入较多苯环刚性结构及适度的交联作用提高了分子内作用力。现场井浆评价证明,微纳米级封堵剂对不同体系性能影响表现基本相同,即对流变性影响不大,对降低API滤失量无效果,对降低HTHP滤失有较明显效果。0.1μm沙盘封堵实验说明,微米级封堵剂对纳米级孔隙基本无封堵作用,微米级刚性颗粒堆叠后形成滤失通道,反而造成纳米级孔隙条件下PPT滤失量的增加。

Using styrene and butadiene as comonomers and 2-methyl-2-acrylic acid-2-hydroxyethyl phosphate(HEMAP)as a coupling agent,a nanoscale plugging agent NPS was synthesized by grafting polymer shell on the surface of fumed nano-silica by emulsion polymerization.The polymerization products were characterized by nuclear magnetic resonance,thermal weight loss,transmission electron microscopy,laser particle size analysis and other methods.'The characterization analysis proved that the monomers were effectively polymerized,and the reaction formed regular and flexible microspheres.The median particle size of the emulsion was 93nm.In addition to the bridging and plugging effect,the hydrophilic groups on the surface of the microspheres also produced multi-point adsorption with the clay minerals in the formation,making the plugging layer denser and the nanoemulsion temperature resistance better,which was because the introduction of more benzene ring rigid structure and moderate crosslinking in the molecular structure improved the intramolecular force.The field well slurry evaluation proved that the micro nanoscale plugging agents had basically the same effect on the performance of different systems,that is,they had little effect on rheology,had no effect on reducing API filter loss,and had obvious effect on reducing HTHP filter loss.The 0.1μm sand table plugging experiment showed that the micron-scale plugging agents basically had no plugging effect on the nanoscale pores.'The stacking of micron-scale rigid particles formed a filtration channel,which caused the increase of PPT filtration loss under the condition of nanoscale pores.