Commonly used borate crosslinkers produce weak fracturing fluids at high temperature, high pressure, high salinity, and low pH conditions. Accordingly, zirconium crosslinkers were developed to address these shortcomings. Zirconium crosslinking chemistry is complicated and depends on many factors such as pH, ionic strength, ligand type, ligand order, and ligand to metal ratio. This work evaluated the rheological performance of four commercial zirconium crosslinkers with a polysaccharide and a polyacrylamide. The tested crosslinkers are manufactured with similar zirconium content but differ in ligand type and ligand order, producing different crosslinker chemical structures. The rheological performance was assessed using an HPHT rheometer at 93–204°C for 1.5 h. Shear tolerance performance was evaluated under shear rates of 40 s⁻¹–1000 s⁻¹. The results showed substantial variation in crosslinking performance due to the differences in the crosslinker chemical structure and type of polymer used. Zirconium lactate and propylene glycol crosslinker exhibited the greatest enhancement in shear and thermal stability with the polysaccharide-based fracturing fluid. Remarkably, the same crosslinker performed the least with the polyacrylamide-based fracturing fluid. However, Zirconium triethanolamine and lactate demonstrated considerable improvements in shear and thermal stability with the polyacrylamide-based system. The work unravelled the influence of the zirconium crosslinker ligand type and ligand order on the rheological properties of both tested polymers. The performance evaluation showed that shear resistance, crosslinking delay, and thermal stability could be improved by utilizing the appropriate crosslinkers. The enhancements ultimately reduce additional additives required, prevent screenouts, and save cost during field treatments.

中文翻译：

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锆交联剂化学结构和聚合物选择对交联压裂液性能的影响

常用的硼酸盐交联剂在高温、高压、高盐度和低pH条件下产生弱压裂液。因此，开发了锆交联剂来解决这些缺点。锆交联化学很复杂，取决于许多因素，例如 pH 值、离子强度、配体类型、配体顺序和配体与金属的比例。这项工作评估了四种商业锆交联剂与多糖和聚丙烯酰胺的流变性能。测试的交联剂具有相似的锆含量，但配体类型和配体顺序不同，产生不同的交联剂化学结构。使用 HPHT 流变仪在 93–204°C 下 1.5 小时评估流变性能。在 40 秒的剪切速率下评估抗剪性能^-1 –1000 秒^-1. 结果表明，由于交联剂化学结构和所用聚合物类型的不同，交联性能存在很大差异。乳酸锆和丙二醇交联剂对多糖压裂液的剪切和热稳定性表现出最大的增强。值得注意的是，相同的交联剂对聚丙烯酰胺基压裂液的影响最小。然而，三乙醇胺锆和乳酸锆在聚丙烯酰胺基系统的剪切和热稳定性方面表现出显着改善。这项工作揭示了锆交联剂配体类型和配体顺序对两种测试聚合物的流变性能的影响。性能评价表明，剪切阻力、交联延迟、通过使用适当的交联剂可以提高热稳定性。这些改进最终减少了所需的额外添加剂，防止了筛分，并在现场处理期间节省了成本。