硼修饰纳米二氧化硅交联剂研发及性能评价

针对目前常规有机硼、无机硼交联的瓜胶压裂液普遍存在羟丙基瓜胶用量大、残渣含量高等的问题，笔者先将硅酸钠水解制得纳米二氧化硅，然后将制得的纳米二氧化硅与γ-氨丙基三甲氧基硅烷反应得到表面修饰纳米二氧化硅，再与硼酸进行反应，最后制得可交联的硼修饰纳米二氧化硅交联剂，该交联剂粒径主要分别在7～11 nm，可有效降低瓜胶用量及残渣含量。研究了该交联剂交联的羟丙基瓜胶压裂液，室内研究表明，该压裂液体系各项性能良好:在温度分别为50℃、120℃，剪切速率170 s-1下连续剪切120 min，最终黏度均大于50 mPa·s；50℃下破胶60 min，破胶液黏度小于5mPa·s；表面张力22.77 mN/m；防膨率89.6%；残渣含量145 mg/L；岩心基质渗透率损害率为9.82%～14.86%，压裂液各项性能良好，羟丙基瓜胶浓度降低20%，残渣含量降低25%，满足现场施工要求。 

Development and Performance Evaluation of a Boron-modified Nanosilica Crosslinking Agent

Field application of guar gum fracturing fluid treated with organoboron and inorganoboron crosslinking agents has been faced with problems such as large amount of guar gum consumed and high residue content of the fracturing fluid. In laboratory research on these problems, nanosilica was first made by the hydrolysis of sodium silicate, and the nanosilica made was then reacted with γ-aminopropyltrimethoxysilane to produce a surface modified nanosilica. The surface modified nanosilica was further reacted with boric acid to produce a boron-modified nanosilica crosslinking agent with particle sizes between 7 nm and 11 nm, and it was able to effectively reduce the amount of guar gum required in mixing fracturing fluid and the residue of fracturing fluids. Study was done on the performance of a hydroxypropyl guar gum fracturing fluid treated with the boron-modified nanosilica as a crosslinking agent, and it was found that the fracturing fluid had good properties. At temperatures 50℃ and 120℃ respectively, shearing of the fracturing fluid at 170 s-1 for 120 min produced a fracturing fluid with viscosity of greater than 50 mPa.s. At 50℃, after gel breaking for 60 min, the fracturing fluid had viscosity that was less than 5 mPa.s and surface tension of 22.77 mN/m. Core swelling test with the gel-broken fracturing fluid showed that the percent core swelling was 89.6% and the residue content was 145 mg/L. Permeability impairment of a core matrix tested with the fracturing fluid was between 9.82% and 14.86%. Other properties of the fracturing fluid were all satisfactory, the amount of hydroxypropyl guar gum required for mixing fracturing fluid was reduced by 20%, and the residue content of the fracturing fluid mixed was reduced by 25%, satisfying the needs of field operations.