高矿化度下特殊黏弹性流体的性能评价及驱油机制研究

采用黏度计、流变仪、动态光散射仪和扫描电镜,对交联聚合物凝胶和聚合物溶液的黏度、分子聚集体、分子线团尺寸(Dh)和黏弹性及其影响因素进行研究。采用岩心流动实验和调驱实验装置,评价交联聚合物凝胶的流动性和调剖能力。结果表明:调整溶剂水矿化度、聚合物和交联剂质量浓度可以使聚合物溶液中生成以分子内交联为主的凝胶或以分子间交联为主的凝胶,分子内交联会使交联聚合物凝胶黏弹性大幅度增加,分子间交联对黏弹性影响较小,交联反应先发生分子内交联,然后演变为分子间交联;黏弹性不仅能够提高洗油效率,而且能够提高微观波及系数;与相同质量浓度聚合物溶液相比,分子内交联聚合物凝胶的黏度接近,Dh略大,黏弹性、阻力系数和残余阻力系数明显增大,具有较高的驱油效率。

Performance evaluation and oil displacement mechanism of special viscoelastic fluid in high salinity media

The viscosity, molecular aggregated state structure, molecular coil dimensions, viscoelasticity and influence factors of the partially hydrolyzed polyacrylamide (HPAM) and the Cr³⁺ crosslinking polymer solution were studied by using Bush viscometer, rheometer, dynamic light scattering and scanning electron microscope. The flow characteristics and profile modification of crosslinking polymer were evaluated using core flow and flooding experiments. The results show that intramolecular crosslinking reaction and intermolecular crosslinking reaction both could take place by adjusting the solvent salinity and crosslinking agent mass concentration. The intramolecular crosslinking would make the system viscoelasticity increase obviously, but the intermolecular crosslinking has a little influence on the viscoelasticity. The intramolecular crosslinking reaction occurs first, and then intermolecular crosslinking reaction occurs. And the viscoelasticity not only could improve cleaning efficiency, but also could expand the microcosmic sweep coefficient. Compared with the same concentration polymer solution, the viscosity of intramolecular crosslinking polymer gel is similar, but the molecular coil dimensions, viscoelasticity, drag coefficient and residual drag coefficient of intramolecular crosslinking polymer gel are greater, so high oil displacement efficiency can be obtained.