纳米ZnO对CTAC蠕虫状胶束流变性能的影响

Effect of Nano ZnO on Rheology of CTAC Wormlike Micelle

纳米材料独特的表面性质可以使材料改性,从而生产出性能优越、满足不同需要的油田化学添加剂。以十六烷基三甲基氯化铵(CTAC)为主要原料,研究了纳米ZnO通过拟交联作用,对CTAC蠕虫状胶束黏度、耐温和降滤失性能的影响,分析了其作用机理。研究结果表明,水杨酸钠与CTAC的物质的量比为1.25∶1时,体系形成最大长度的蠕虫状胶束,黏度达到最大;纳米ZnO能够改善CTAC黏弹性胶束溶液的黏度、热稳定性和剪切稳定性,尤其在中低温增黏效果显著,90℃高温时仍有增黏作用,改性体系黏度可以保持在60 m Pa·s;优化得出纳米ZnO的质量分数为0.2%时对体系增黏效果最好;具有极高比表面积的纳米ZnO很容易吸附在胶束表面,屏蔽了胶束之间的静电排斥作用,使CTAC胶束形成一种更加稳定的三维网状结构;改性体系符合Maxwell流体模型,是具有单一松弛时间的线性黏弹性流体。

The unique surface natures of nano materials make them suitable for modification to produce oilfield chemicals of excellent performance. The optimum ratio is studied that cetyltrimethyl ammonium chloride（CTAC）, a clean fracturing fluid additives commonly used in China, to form worm-like micelle with sodium salicylate（Na Sal）. Nano ZnO was used to modify the property of the worm-like micelle solution through quasi-crosslinking, and the mechanism of nano ZnO in enhancing the viscosity, thermal stability and shearing stability was analyzed. The mass fraction of ZnO needed for the modification was optimized. In laboratory experiments, the viscosity of the micelle solution reached the maximum value at CTAC∶Na Sal = 1.25∶1（molar ratio）, and so does the length of the micelle. The micelle solution has the best viscosifying performance at 0.2% of ZnO, and the viscosity of the solution is maintained at 60 mPa·s at 90 ℃, even after long time of shearing and heating. CTAC micelle solution modified with nano ZnO shows elasticity as a whole, and its rheological behavior conforms to Maxwell rheological model, as demonstrated by Cole-Cole fitting. This micellesolution is a linear viscoelastic fluid with single relaxation time.