Abstract: Drag reduction performance of slick water is one of the key factors affecting fracturing, but the physical mechanism has still not been clearly identified. This paper aims to build a drag reduction modeling of polymer additives dissolved in hydrocarbon in pipe flow on the basis of Giesekus constitutive equation, which was validated by the loop experiment later. The model was applied to calculate the drag reduction rate of polyacrylamide tetrapolymer additive (DR800) in turbulent flow. Indoor loop experiments were introduced for parameter validation and model verification. Although the physical mechanism has still not been clearly identified, the modeling was aimed to explain the contribution of different components: viscous shear stress, Reynolds shear stress and viscoelastic shear stress. It turned out that as the complexity of the flow increased, the viscous contribution and viscoelastic contribution decreased while the turbulence contribution increased. In low Reynolds numbers, viscoelastic shear stress contributed most to friction coefficient while the turbulence can be neglected. In high Reynolds numbers, the contribution of turbulence increased rapidly thus to be the dominating part of the overall contribution, followed by viscoelasticity, and the least was viscous shear stress. By performing consistent comparisons between modeling and experimental results, it can be seen that the model can predict the drag reduction rate of DR800 in a range, which can be used for field production and guidance.

Key words: Drag reduction, Turbulent, Pipe flow, Polymer, Shear stress

摘要： 滑溜水减阻性能是影响压裂成功的关键因素之一，但其减阻机理尚未明确。通过数值模拟并结合实验研究圆管中聚合物减阻剂减阻机理，以Giesekus本构方程为基础，建立简化的计算流体模型计算湍流管道中聚丙烯酰胺四元共聚物添加剂（DR800）的减阻率。通过室内环路实验对此模型进行参数确认和验证。此模型可用来解释黏性剪切应力、雷诺剪切应力和黏弹性剪切应力等不同组分对摩阻的贡献。结果表明，随着雷诺数增加，黏弹性贡献和黏性贡献降低，而湍流贡献增加；低雷诺数下，黏性剪切应力和黏弹性剪切应力对摩阻贡献最大，而黏弹性贡献可以忽略；高雷诺数下，湍流贡献最大而黏性贡献最少。通过对比模型结果和室内实验结果以及应用现场情况可知，此模型在一定范围内可预测DR800的减阻率，并用于现场生产与指导。

关键词: 减阻率, 　湍流, 　管流, 　聚合物, 　剪切应力