非均质多孔介质中剪切稀释流的非混相驱替研究

地下流体在一定温度压力条件下,会呈现剪切稀释性。剪切稀释性影响流体黏度场,从而改变流体被驱替时的特征。使用植入幂律流变模型的格子Boltzmann两相流模型,编写计算程序,模拟牛顿流体在非均质多孔介质中驱替剪切稀释流的过程。使用非牛顿泊肃叶流验证了数值模型,并从界面推进、驱替效率、速度场、黏度场等方面研究非均质多孔介质中被驱替液的剪切稀释性对驱替过程的影响。模拟结果显示:被驱替液剪切稀释性的增强造成驱替界面推进的加快和驱替效率的提升,使驱替液更能深入驱替非均质多孔介质中残余的被驱替液。该现象的机制为:被驱替液剪切稀释性的增强造成了指进路径上的黏度降低,而非指进区域的黏度升高;驱替过程由指进路径上高流动区域的黏度所主导,因此增强被驱替液剪切稀释性的效果类似于降低黏度,从而提升驱替效率。研究揭示了流体剪切稀释性对多孔介质中驱替过程的影响,对涉及地下非牛顿流体驱替过程的产业具有指导性。

抗溶泡沫液流变特性及管流摩阻损失分析

针对抗溶泡沫液管流摩阻损失计算中涉及的非牛顿及流变学问题,利用控应力流变仪对抗溶水成膜泡沫液和抗溶氟蛋白泡沫液(3%型、6%型)的流变特性进行了实验研究。结果表明,抗溶泡沫液具有显著的剪切稀释性,其平衡流变曲线符合Herschel-Bulkley模型。随着测试温度的降低,抗溶泡沫液的表观黏度、动屈服应力和稠度系数均增大,流动行为指数减小,剪切稀释性增强。抗溶泡沫液圆管层流摩阻损失可通过理论计算式求得,流态判断和紊流摩阻损失可采用Hanks方法进行计算。

Modified expression for the effective viscosity in the semi-dilute shear flows of fiber suspension

The available expressions for the effective vis-cosity can not provide good predictions compared with the experiment data measured in the semi-dilute shear flows of fiber suspension with small aspect ratio. The departure of the theoretical prediction from the measured data increases with the decrease of the fiber aspect ratio. Therefore, by experi-ment for the fiber with 20 mm diameter, a new expression for the effective viscosity in the semi-dilute shear flows of fiber suspension with small aspect ratio is proposed, the relation-ship between the shear viscosity of fiber suspensions and the fiber concentration is given. The results show that the effec-tive viscosity is not a linear function of the fiber concentra-tion.