A High Temperature Shear-resistant Association Supramolecular Polymer Weak Gel Fracturing Fluid
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摘要: 超分子聚合物化学是超分子化学与高分子化学相互交叉融合形成的新方向，因此基于前期对超分子压裂液的研究成果，采用对疏水单体增溶性能好的ASF-1两性离子表面活性剂，与自制的LCM长碳链阳离子不饱和成链单体、自制的HTM抗高温单体等进行胶束共聚合反应，合成了一种高温耐剪切的超分子聚合物稠化剂SPM-2。通过复配具有蠕虫状胶束的物理交联剂PCA-1，制备出一种超分子缔合弱凝胶压裂液（0.8% SPM-2+0.5% PCA-1）。该压裂液具有超分子“蜂巢”网格结构，表观黏度随物理交联剂加量增大而持续增加，达到了胶束与聚合物链的强物理交联效果。该压裂液在150℃、170 s-1、2 h下表观黏度保持在58 mPa·s左右，相比超分子聚合物溶液提高了30 mPa·s ；剪切速率从40 s-1增至1 000 s-1，再降到40 s-1后，压裂液黏度迅速降低并快速恢复，剪切回复性好；在0.01~10 Hz内进行频率扫描，压裂液弹性明显优于黏性；支撑剂沉降速率小于8×10-3 mm/s，悬砂能力相比稠化剂溶液提高了一个数量级；在90℃、2 h下破胶液黏度小于2 mPa·s，未检出残渣；岩心伤害率小于10%。室内实验结果表明，该压裂液可满足致密砂岩气藏高温储层压裂需求。Abstract: Supramolecular polymer chemistry is a new interdiscipline of supramolecular chemistry and polymer chemistry. Based on the research work previously done on supramolecular fracturing fluid, a high temperature shear-resistant supramolecular polymer viscosifer, SPM-2, has been synthesized with a zwitterionic surfactant ASF-1 (having good solubilization to hydrophobic monomers), a synthesized long-chain unsaturated cationic monomer, LCM, and another synthesized high temperature monomer HTM, through micelle copolymerization. By compounding the synthesized SPM-2 and PCA-1 (a physical crosslinking agent with worm-like micelle), an association supramolecular polymer fracturing fluid (0.8% SPM-2+0.5% PCA-1) with weak gel has been developed. This fracturing fluid has supramolecular "honeycomb" grid structure, and apparent viscosity that increase with increase in the concentration of PCA-1. It has been proved that ASF-1 and LCM formed strong physical crosslinking. Sheared at 150℃ and 170 s-1 for 2 h, the apparent viscosity of the fracturing fluid was maintained at about 58 mPa.s, higher than the apparent viscosity of the SPM-2 solution itself by 30 mPa.s. Increased the shear rate frst from 40 s-1 to 170 s-1, and then reduced the shear rate to 40 s-1 again, the viscosity of the fracturing fluid was reduced and resumed sharply, showing good resistance to shearing. Scanned at frequency of 0.01-10 Hz, the elasticity of the fracturing fluid was better than its viscosity. The settling rate of proppant in the fracturing fluid was less than 8×10-3 mm/s. Compared with the supramolecular polymer SPM-2, this fracturing fluid has suspending capacitythat is an order of magnitude higher. The fracturing fluid, after gel-breaking at 90℃ for 2 h, had viscosity less than 2 mPa·s, and no residue had been found therein. Core experiment indicated that core damage by the fracturing fluid was lower than 10%. Laboratoryexperiments showed that this fracturing fluid can satisfy the needs for fracturing high temperature tight sand gas reservoirs.
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