加重压裂液用聚合物稠化剂合成及性能

加重压裂液是解决施工压力过高的有效手段之一，普通瓜胶加重压裂液残渣含量较高、对地层伤害较大，而VES类压裂液又受到使用温度的限制，无法应用于高温井压裂施工。针对上述问题，利用水溶液聚合法合成了一种AM/CnDMAAC/NVP超分子聚合物BC40。通过对特性黏数和溶解性能的评价，结合正交实验与单因素法对聚合条件进行了优化，得到最佳聚合条件为:聚合单体总浓度为30%、引发剂浓度为0.12%，聚合温度为35℃，通氮排氧1 h，反应时间5 h。BC40在甲酸钠加重的水溶液中具有良好的增黏能力。配制不同密度的加重压裂液在120℃、170 s-1条件下剪切2 h，表观黏度稳定在30 mPa · s以上，表现出良好的耐温耐剪切性能；向不同密度的加重压裂液中加入破胶剂，在95℃下均可破胶，得到的破胶液表面张力低，破胶后残渣含量低，对地层伤害小。 

Synthesis and Performance of a Polymeric Thickening Agent for Weighted Fracturing Fluids

Weighted fracturing fluid is one of the effective methods to deal with high formation pressure encountered during fracturing operation. In mixing weighted fracturing fluids, normal guar gum will leave high concentrations of residues in the fracturing fluids, causing high formation damage. The VES type fracturing fluid has low temperature stability, therefore is unable to be used in high temperature environment. To resolve these problems, a supramolecular polymer BC40 has been synthesized with AM/CnDMAAC/NVP through water solution polymerization. By evaluating the intrinsic viscosity and solubility of the synthesizing products, and through orthogonal experiment and single-factor method, the optimum synthesis condition was obtained, as follows:the total concentration of the monomers of 30%, concentration of the initiator of 0.12%, temperature for the polymerization of 35℃, time for exhausting oxygen by introducing nitrogen of 1 h, and reaction time of 5 h. In a water solution weighted with sodium formate, BC40 performed very well as a viscosifier. Fracturing fluids of different densities mixed at 120℃ and 170 s-1, had apparent viscosity of more than 30 mPa·s after being sheared for 2 h, showing good high temperature shearing performance. The gel structure formed in these weighted fracturing fluids can all get broken after treatment with gel breaking agent at 95℃. The fracturing fluids, after gel breaking, had low surface tension and low residue contents, and therefore had low damage to the formations fractured.