胶凝原油的黏弹性流变模型

The Rheological Model in View of the Viscoelastic Properties for the Gelled Crude Oil

流变模型是工程计算的基础。为了研究胶凝原油的启动屈服过程,确定胶凝原油的黏弹性流变模型至关重要。经典的黏弹性固体模型(如标准线性体)和黏弹性流体模型(Burgers模型),在蠕变初期不能精确拟合胶凝原油的蠕变实验曲线,分数指数模型在蠕变的后半段存在偏差。根据胶凝原油的蠕变和松弛特性,由Maxwell体和具有分数阶导数的类Kelvin体组合建立了具有黏性流的黏弹性固体模型,利用Laplace变换和反演推导得到了该模型的蠕变柔量表达式。实验结果显示,该模型能精确描述胶凝原油的蠕变过程,而且直观易懂、应用方便、物理概念清晰。

The rheological behavior of the gelled crude oil affects directly the restart of the pipeline system after shutdown,which plays a very important role in the safety of the pipeline.To choose a suitable viscoelastic rheological model,which is the basis of engineering calculations,is vital for the study on the restart yielding properties of the gelled crude oil.The classic models for the viscoelastic solid（such as standard linear body） and for fluids（Burgers model） are incapable of fitting the experimental creeping curves precisely in the early stage of the creeping of gelled crude oil.Furthermore,the fractional exponential model deviates from the experimental creeping curves in the creeping latter stage.According to the creeping and relaxation properties of the gelled crude oil,a new viscoelastic solid model with viscous flow was established by combining the Maxwell component and quasi-Kelvin component having fractional order derivatives.The creep compliance expression of the model was derived by using Laplace transform and inversion.The new model proposed is capable of describing the creeping process of the gelled crude oil and fits well with the experimental data.The physical conception of the model proposed is clear and easy to be understood,at the same time the application of the model is convenient too.