Abstract The performance of polymer gel to plug a hydraulic fracture is greatly affected by its distribution patterns and gelling effect. In this study, the migration of a gel plugging agent in a fracture and its plugging after gelling were investigated by physical simulation experiments. In addition, the distribution patterns of the gel plugging agent and its plugging mechanism after gelling were investigated in detail. The results of this study revealed that the migration flowing behavior of the gel solution in a fracture can be divided into three streams: fracture flow, leak off flow, and matrix flow. Such behavior distributed the gel in three different patterns after gelling: gel clusters in the fracture, gel layer on the fracture surface, and dispersed gel lumps in the matrix pores-throats. Because of the leak off flow and the difference in components, the gel solution has apparent disproportional leak off–diffusion of components during its migration in a fracture, with less polymer molecules and loss of more cross-linking agent ions. The leak off of the cross-linking agent significantly deteriorates the gelling strength of the polymer gel, affecting its performance to plug a hydraulic fracture. The results also show that when the normalized concentration of the cross-linking agent ions in a fracture is less than 0.6, gel fails to plug the fracture effectively after gelling. When gelling was carried out by in situ cross-linking, polymer gel provided more satisfactory plugging performance than the gelling via ground pre-cross-linking.

中文翻译：

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聚合物凝胶用于水力压裂堵水的堵漏机理

摘要 聚合物凝胶封堵水力裂缝的性能受其分布模式和胶凝效果的影响很大。本研究通过物理模拟实验研究了凝胶封堵剂在裂缝中的迁移和凝胶化后的封堵。此外，还详细研究了凝胶堵剂的分布规律及其凝胶化后的堵漏机理。研究结果表明，凝胶溶液在裂缝中的运移流动行为可分为三种流：裂缝流、泄漏流和基质流。这种行为在凝胶化后以三种不同的模式分布凝胶：裂缝中的凝胶簇，裂缝表面的凝胶层，以及基质孔喉中分散的凝胶块。由于渗漏流和组分的差异，凝胶溶液在裂缝中迁移过程中存在明显的不成比例渗漏-组分扩散，聚合物分子较少，交联剂离子损失较多。交联剂的泄漏会显着降低聚合物凝胶的胶凝强度，影响其堵塞水力裂缝的性能。结果还表明，当裂缝中交联剂离子的归一化浓度小于0.6时，凝胶无法有效封堵裂缝。当通过原位交联进行胶凝时，聚合物凝胶提供了比通过地面预交联胶凝更令人满意的堵漏性能。凝胶溶液在裂缝中迁移过程中具有明显的不成比例泄漏-组分扩散，具有较少的聚合物分子和更多的交联剂离子损失。交联剂的泄漏会显着降低聚合物凝胶的胶凝强度，影响其堵塞水力裂缝的性能。结果还表明，当裂缝中交联剂离子的归一化浓度小于0.6时，凝胶无法有效封堵裂缝。当通过原位交联进行胶凝时，聚合物凝胶提供了比通过地面预交联胶凝更令人满意的堵漏性能。凝胶溶液在裂缝中迁移过程中具有明显的不成比例泄漏-组分扩散，具有较少的聚合物分子和更多的交联剂离子损失。交联剂的泄漏会显着降低聚合物凝胶的胶凝强度，影响其堵塞水力裂缝的性能。结果还表明，当裂缝中交联剂离子的归一化浓度小于0.6时，凝胶无法有效封堵裂缝。当通过原位交联进行胶凝时，聚合物凝胶提供了比通过地面预交联胶凝更令人满意的堵漏性能。交联剂的泄漏会显着降低聚合物凝胶的胶凝强度，影响其堵塞水力裂缝的性能。结果还表明，当裂缝中交联剂离子的归一化浓度小于0.6时，凝胶无法有效封堵裂缝。当通过原位交联进行胶凝时，聚合物凝胶提供了比通过地面预交联胶凝更令人满意的堵漏性能。交联剂的泄漏会显着降低聚合物凝胶的胶凝强度，影响其堵塞水力裂缝的性能。结果还表明，当裂缝中交联剂离子的归一化浓度小于0.6时，凝胶无法有效封堵裂缝。当通过原位交联进行胶凝时，聚合物凝胶提供了比通过地面预交联胶凝更令人满意的堵漏性能。