含蜡原油的动屈服应力

The Dynamic Yield Stress of Waxy Crude Oil

在温度低到一定程度时,含蜡原油存在着屈服应力。介绍了动屈服应力物理意义及概念的引伸,指出动屈服应力是维持物料继续流动所需要的最小剪切应力,由平衡流变曲线外延确定,反映了含蜡原油经过破坏后不能完全恢复的残余结构的强度,不是唯一值。对含蜡原油动屈服应力的测量,通常采用的方法有直接法和间接法,间接法中的应力松弛法被认为是一种较好的测量方法。胜利油田原油动、静屈服应力的测量值与预剪切过程中选用的剪切率有关,由平衡流变曲线外延得到的动、静屈服应力之间存在着很大差别。介绍了动屈服应力在含蜡原油低温输送和含蜡原油停输后再启动过程中的应用。

Yield stress exists in waxy crude oil when temperature drops to a certain point. The dynamic yield stress is described and is defined as the minimum shear stress necessary for keeping the products flow on. Dynamic yield stress is determined by the extension of the equilibrim rheological characteristics. Having more than one values ,it presents the strength of the nonrecover-able,residual structure of the destructed waxy crude oil. Two methods,direct and indirect methods,are usually involved in the measurement of waxy crude oil's dynamic yield stress. Stress relief method is one of the best ways in indirect measurement. The measured dynamic/static yield stresses of the crude oil from Shengli Oilfield depend upon the shear rate selected during pre-shearing,and they differ greatly from the stress values obtained from the extention of equilibrim rheologic characteristics. Introduced arc the applications of dynamic yield stress in low temperature transportation as well as in the course of restart after shutdown of the waxy crude oil transport system.