钻井液用纳米苯丙乳液封堵剂的制备与性能研究

Preparation and performance study of nano styrene-acrylate emulsion plugging agent for drilling fluid

摘要:

针对深层泥页岩地层纳微米孔缝引发的井壁失稳问题，采用半连续种子乳液聚合法，以苯乙烯、丙烯酸丁酯、丙烯酸、丙烯酰胺、2-丙烯酰胺-2-甲基丙磺酸为单体合成纳米苯丙乳液封堵剂，并进行结构表征与性能评价。结果表明，该乳液中位粒径D₅₀为174.5 nm，呈单峰分布，颗粒呈球状或近球状，分散稳定，固相含量高于80%；在180 ℃老化16 h后，高温高压滤失量随乳液加量增加而降低，API滤失量在加量2.5%时最低，综合降滤失效果与经济性，最优加量为2.5%，滤饼更薄更致密，滤饼清水滤失量降低率达41.7%；该乳液与钻井液常用处理剂配伍性良好，150 ℃老化后加纳米乳液体系较未加体系，高温高压滤失量由15.3 mL降至13.2 mL，10 μm砂盘滤失量由7.2 mL降至5.6 mL，对微米级裂缝具有良好的封堵效果，改善滤饼质量，有利于井壁稳定。

Abstract:

To address the wellbore instability caused by nano-micro-scale pores and fractures in deep shale formations， a nano styrene-acrylate emulsion plugging agent was synthesized via semi-continuous seed emulsion polymerization using styrene， butyl acrylate， acrylic acid， acrylamide， and 2-acrylamido-2-methylpropanesulfonic acid as monomers， and its structural characterization and performance evaluation were carried out. The results show that the emulsion has a median particle size （D₅₀） of 174.5 nm with a unimodal distribution； the particles are spherical or nearly spherical and stably dispersed， and the solid content is higher than 80%. After hot-rolling aging at 180 ℃ for 16 h， the high-temperature and high-pressure （HTHP） fluid loss of the drilling fluid decreases with increasing emulsion dosage， while the API fluid loss reaches its minimum at a dosage of 2.5%. Considering both fluid loss control performance and economic efficiency， the optimal dosage is determined to be 2.5%， under which a thinner and denser filter cake is formed and the reduction rate of clear-water fluid loss of the filter cake reaches 41.7%. The emulsion exhibits favorable compatibility with conventional drilling fluid additives. After aging at 150 ℃， compared with the blank system， the HTHP fluid loss of the nano-emulsion-containing system decreases from 15.3 mL to 13.2 mL， and the 10 μm sand-disk fluid loss decreases from 7.2 mL to 5.6 mL， indicating good plugging performance for micron-sized fractures， improved filter-cake quality， and beneficial effects on wellbore stability.