中文摘要：

在石油开采和输送过程中由于石蜡沉积造成的经济损失每年达数十亿美元。添加化学降凝剂的方法可以避免或减小固相沉积造成的不利影响和危害，因此研究降凝剂对石蜡沉积的影响有非常重要的意义。从流变学和晶体学方面对降凝剂影响原油中的石蜡沉积进行了实验研究。实验数据显示，加剂后原油的析蜡点不变，析蜡峰温向低温方向移动，这是因为降凝剂的加入使得蜡晶的晶格结构由正交型转变为了旋转型，延缓了蜡晶的析出速率，且由于加剂后蜡晶颗粒变大，形状更接近于球形、使得蜡晶聚集体的絮凝能力减弱，原油的低温流动性得到了改善。

英文摘要：

Economic loss due to wax precipitation in oil exploitation and transportation has reached several billion dollars a year recently. Addition of pour point depressants （PPD） has been proved to be an efficient way to inhibit wax deposition. It is important to study the effect of PPD on wax precipitation. In this paper, effect of PPD on wax precipitation of Daqing crude oil was studied from the aspects of rheology and wax crystal morphology. The results show that after adding PPD, the wax precipitation temperature is almost constant and the wax precipitation peak temperature of crude oil is shifted to lower temperature. This result is due to that the crystal structure of wax can be partly transformed into hexagonal from orthorhombic form and wax crystallization can be dramatically slowed by PPD The size of paraffin particles increases, and the shape of wax crystal is getting more near to sphericity after adding PPD in crude oil, so the connection capability among paraffin particles is lowered and the flow properties of waxy crude oil at low temoeratures is imoroved.