黄原胶水凝胶的分子网络模型

MOLECULAR NETWORK MODEL OF XANTHAN GUM

本文结合二次采油中作为压裂液的黄原胶水凝胶,从其成胶机理着手分析,以Carreau-Bird模型为基点,在分子网络模型中引进了吸附反应动力学项以及计及流体触变性质的函数f(t),并把自由链、迷向链及破碎网络对应力的贡献模拟成牛顿性,从而导出本构方程。方程中的参数值由凝胶的粘弹性性质及非线性物质函数决定,用有约束的优化方法进行优化后得到,模型计算的结果与实验数据大致相符。

In the paper, we took the xanthan gum, which is widely used in the oil-recovery industry as the'fracturing fluid', as an example and analysed the mechanism of its gelling. Introducing the adsorption reaction and thixotropic function f (t) into the molecular network model and assuming the contribution of the broken pieces of network, the free and stray chains to the toatl stress tensor to be Newtonian, we obtained a constitutive equation on the basis of the carreau-Bird model. The, parameters in the constitutive equation were estimated and optimized according to the experiments data of the linear viscoerasticity and non-Knear material functions of the xanthan gum by using the tolerable multi-surface-body gradient method with constrained conditions. This model can predict the rheological properties which are in agreement with those of the xanthan gum. It is obviously found that the shear viscisity and complex one of the xanthan gum do not obey the Cox-Merz rule in the range of shear rates of these experiments-