Yield stress, as the key parameter to characterize the network strength of waxy oil, is important to the petroleum pipeline safety. Reducing the yield stress of waxy oil is of great significance for flow assurance. In this study, the effect of alternating magnetic field (intensity, frequency) on the yield stress of a waxy model oil with nanocomposite pour point depressant (NPPD) is systematically investigated. An optimum magnetic field intensity and frequency is found for the reduction in yield stress. When adding with NPPD, the heterogeneous nucleation of NPPD contributes to the reduction in yield stress for waxy model oil. Interestingly, the magnetic field is helpful for the modification of yield stress at a lower frequency and intensity before the optimal value; however, the modification is found to be weakened when the magnetic field is further increased after the optimal value. Possible explanation is proposed that the aggregation morphology of wax crystal would be altered and results in the release of wrapped oil phase from the network structure under the magnetic field.

中文翻译：

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磁场和纳米复合降凝剂对蜡质模型油屈服应力的协同作用

屈服应力作为表征蜡质油网络强度的关键参数，对石油管道安全至关重要。降低蜡质油的屈服应力对确保流动性具有重要意义。在这项研究中，系统地研究了交变磁场（强度，频率）对含纳米复合降凝剂（NPPD）的蜡质模型油的屈服应力的影响。找到了最佳磁场强度和频率以降低屈服应力。当添加NPPD时，NPPD的异相成核有助于降低蜡质模型油的屈服应力。有趣的是，磁场有助于降低屈服应力，使其在达到最佳值之前以较低的频率和强度变化。然而，当在最佳值之后进一步增加磁场时，发现修饰变弱。提出了可能的解释，即蜡晶体的聚集形态将被改变，并导致包裹的油相在磁场下从网络结构中释放出来。