pH值对于表面硼改性纳米二氧化钛交联剂交联性能的影响

传统有机硼交联羟丙基瓜胶 （HPG）冻胶压裂液体系具有稠化剂用量大，压裂施工成本高，压裂残渣多，裂缝导流能力差等诸多缺点。为了达到降低压裂液稠化剂用量、提高压裂施工效果的目的， 采用“两步法”制备了一种表面硼改性的纳米二氧化钛颗粒 （NCC）作为HPG压裂液交联剂。研究了pH值对于NCC交联HPG冻胶耐温性能的影响，结果表明随着pH值的增加，NCC冻胶压裂液的耐温性能先增大后减小。所形成的冻胶压裂液在pH=12时耐温性能最佳。与传统有机硼交联剂相比，NCC可大大减小稠化剂用量，NCC交联的0.3 wt.% HPG冻胶在pH值为8~14的范围内均能保持良好的耐温性能。利用扫描电镜表征了NCC冻胶在不同pH值条件下的交联形貌及交联结构，结果表明，在pH值为12时，NCC冻胶微观形貌最致密。

he effect of pH on the crosslinking performance of orgonoboron-modifeid titanium dioxide nanoparticles

Conventional boron crosslinked guar gum hydraulic fracturing fluids are combined with the disadvantages of high polymer loading, large quantity of residue, low regained hydraulic fracturing conductivity and high treatment cost. In order to achieve reduced polymer loading and enhanced hydraulic fracturing treatment, boron modiied titanium nanoparticles (NCC) was synthesized by two-step surface modification. We investigated the effect of pH on the thermal stability of NCC crosslinked HPG gels. The results showed that with pH increasing from 7 to 14, the remaining viscosity increased first and then decreased, the optimal viscosity was achieved at pH=12. Compared with conventional organic borate crosslinker, NCC can reduce the polymer dosage significantly. At polymer loading of 0.3 wt.%, NCC gels maintained superior thermal stability over the pH range of 8 to 14. To investigate the effect of pH on the thermal stability in microdimention, SEM observation was performed. The results showed that the effect of pH on the thermal stability may be attributed to the different morphology of NCC gels at different pH.