含蜡原油特征温度实验研究

Experimental research on characteristic temperature of waxy crude

用旋转粘度计对原油在温度扫描条件下的粘-温关系进行的实验研究表明,原油在低温时呈胶凝状态。根据原油低温凝胶化理论,用常规方法对实验数据进行了处理,得到了动态降温条件下含蜡原油流动性变化的特征温度,即开始出现最大成胶活化能时所对应的温度。对于同一种原油,特征温度越高其低温流动性能越差。对实验数据的分析表明,特征温度与原油经历剪切过程的粘性流动熵产呈幂函数关系,并据此拟合出相应的经验式。利用该经验式,通过计算管输原油过程中所产生的粘性流动熵产,可确定原油的特征温度。6种空白原油及4种加剂原油的92组特征温度数据的计算值与实测值的最大偏差为0.86℃,平均绝对偏差为0.3℃。该关系式可用于管输含蜡原油流动的安全性评价。

The variation of viscosity with temperature was measured by temperature scanning procedures in a coaxial cylinder viscometer. The waxy crude tended to become gel at low temperature. On the basis of gelation theory, the test data was treated by conventional method, and the characteristic temperature of waxy crude was found. The characteristic temperature was corresponding to the maximum value of gelling activity energy. The flow ability of waxy oil at low temperature get weaker as the characteristic temperature gets higher for the same oil. The characteristic temperature and entropy generation of waxy crude generated during pipeline transportation have the power correlation. The empirical relational expression of characteristic temperature versus entropy generation was developed on the basis of test data. Using this relational expression, the characteristic temperature of crude oil can be predicted ,provided that the entropy generation is known. 92 groups of data of characteristic temperature obtained from six virgin crude oils and four PPD -beneficiated crude oils were compared with the predicted values. The maximum absolute deviation of characteristic temperature is 0.86℃ ,and the average absolute deviation of characteristic temperature is 0.3℃. This model can be used to evaluate the flow assurance of crude oil in pipelines.