动态剪切对含蜡原油触变性的影响

Study on the Influence of Dynamic Shear on Thixotropy of Waxy Crude Oil

含蜡原油在管道运输的过程中由于与周围环境存在温差以及管道剪切作用,往往会使管道内原油经历动态剪切过程,因此会对原油低温触变性特性造成一定的影响。为了分析原油降温过程中施加恒剪切速率对含蜡原油触变性的影响,对油样在降温过程中施加一恒定剪切速率并进行滞回环触变性实验,以滞回环曲线面积大小量化描述胶凝体系触变性结构的强弱。结果表明:动态剪切对原油触变性的影响很依赖于终冷温度的大小,并且在一定的剪切速率范围内,动态剪切速率越大的油样触变性结构越强;推导并计算了VT550流变仪内黏性流动熵产的公式和大小,结果表明黏性流动熵产的大小也能判断原油的触变性特征。

Due to the temperature difference between the crude oil and the surrounding environment and the shearing effect of the pipeline during the transportation of waxy crude oil,the crude oil in the pipeline often undergoes a dynamic shearing process,which will affect the low-temperature thixotropy characteristics of the crude oil.In order to analyze the effect of constant shear rate on the thixotropy of waxy crude oil during the cooling process of crude oil,a constant shear rate was applied to the oil sample during the cooling process and the hysteresis loop thixotropy experiment was performed.In the experiment,the strength of thixotropic structure of gelling system was quantitatively described by the size of hysteresis curve area.The results showed that the effect of dynamic shear on the thixotropy of crude oil depended on the final cooling temperature.In a certain range of shear rate,oil samples with higher dynamic shear rate had stronger thixotropic structure;the formula and size of the viscous flow entropy production in the VT550 rheometer were derived and calculated.The results showed that the viscous flow entropy production could also reflect the thixotropic characteristics of crude oil.