基于匀变速剪切对含蜡原油触变性的研究

Study on Waxy Crude Oil Thixotropy Based on the Uniform Variable Shear

含蜡原油的胶凝问题是管道运输过程中一个重要的研究问题。通过对经历不同降温速率温度降至凝点附近的原油做匀加速剪切,剪切至某值后再做匀减速剪切,形成一个环形剪切。测量剪切应力随剪切速率变化的曲线关系,结果表明:在这样循环匀变速剪切的作用下,样品的剪切应力各点连线也呈现一个环形,即称作含蜡原油的滞回环。在胶凝原油发生屈服之前,剪切应力随剪切速率增大急剧增大,持续的剪切会有效阻止蜡晶结构的形成;降温速率越低,原油形成的蜡晶结构强度越大。

The problem of waxy crude oil gelling is an important research problem in the process of pipeline transport. In this experiment, uniformly accelerated shear of crude oil whose temperature was dropped to freezing point by different cooling rate was carried out; after the shear rate reached to the maximum value, uniform deceleration shear was carried out to form a cyclic shear. The relationship between the shear stress and shear rate change was measured. The results show that： under the action of such a cycle uniform variable shear, the attachment of each shear stress point of sample also presents a ring, which is called the hysteresis loop of waxy crude oil. Before the gelled crude oil yields, shear stress increases sharply with the increase of shear rate, and constant shear will effectively prevent the formation of wax crystal structure; the lower the cooling rate, the higher the wax crystal structure strength.