剪切稀化非牛顿流体气液两相流界面波动特性

Predicting multiphase flow behavior in wellbores is of vital importance for the development of technologies and theories in deep-water drilling and completion. Fluids in wellbores display non-Newtonian effects and their rheology exerts a strong influence on flow patterns, interface fluctuation, pressure drop, heat transfer and many other flow characteristics. Due to the complexity of non-Newtonian rheology, profound knowledge of flow structures and interfacial wave behaviors in gas/non-Newtonian two phase flow is not well documented in the existing literature, which is of great interest in industrial applications. In this project, experimental and numerical approaches are conducted to study the dynamics of the interfacial waves in two-phase gas/shear-thinning fluid pipe flows. An experiment is performed on temporal/spatial variations of phase distributions over the pipe under various flow conditions. We investigate the effect of shear-thinning on the flow structures of each flow pattern and interfacial wave’s types, shapes, movement, interaction, deformation and breakup mechanism. Additionally, we employ the power-law rheological model to characterize the shear-thinning fluid and develop numerical models, based on the force analysis, for wave behaviors, deformation and breakup. According to the effect of the rheology of shear-thinning fluid on the flow pattern transitions and pressure distribution, a new solution is proposed for flow control in pipes. The study in this proposal will enrich the fundamental theories of multiphase flow in wellbores and provide theoretical support for deep-water drilling and completion.

井筒多相流动规律是深水开发风险评估及深水油气井筒压力精细控制所必需的理论基础。井筒内流体大多具有非牛顿剪切稀化特性，剪切应力随流速改变造成井筒内气液两相流独特的相界面宏观结构和各相宏观分布的状态特征，各相间的动量、质量、能量传输机理与定量规律都与牛顿流体有较大差别。本项目针对剪切稀化非牛顿流体流变性对两相流相界面结构及界面波动特性的影响机理这一关键问题开展深入研究。采用机理实验和理论分析相结合的方法，获得剪切稀化非牛顿流体气液两相流各流型的宏观相界面分布特征，查清剪切稀化非牛顿气液两相流内界面波种类、运动特性、形变规律及破碎机理,揭示非牛顿流体流变性对流型转变的影响机制，提出管内流动特征及压力分布调控的新方法。本项目研究成果将丰富井筒多相流动规律的理论认识, 为提高岩屑携带能力，降低循环压力损失，减少筒壁流动冲刷，防止井涌、井喷等井控手段提供理论支撑，具有重要的学术价值和应用前景。

井筒多相流动规律是深水开发风险评估及深水油气井筒压力精细控制所必需的理论基础。本项目采用机理实验和理论分析相结合的方法，对剪切稀化非牛顿流体气液两相流内流型特征、流型转变机理、流动阻力特性、界面波运动特性和流致振动特性等基础科学问题开展了系统研究。绘制了剪切稀化非牛顿流体气液两相流流型图，发现流体剪切稀化特性削弱了液膜振荡特性从而抑制了搅拌流的产生，阐明了流体流变性相界面宏观特性的影响机制；建立了剪切稀化非牛顿流体气液两相搅拌流含气率和压降预测模型，揭示了流体流变性对相分布、含气率和压力梯度的影响规律；提出了通过提取液膜厚度时空分布的界面波图像识别新技术，获得了界面波种类、运动特性及相互作用规律，发现流体剪切稀化特性的增强会抑制纹波的产生并强化扰动波对相界面动态演化的影响；建立了界面波运动生长模型，揭示了剪切稀化非牛顿流体气液两相搅拌流被抑制的内在原因；提出了流型转变新机理和新判据，基于Kelvin-Helmholtz不稳定性，建立了幂律流体弹状流向搅拌流转变数理模型，揭示了界面波运动特性和流体流变性对流型转变的影响机理；基于频谱分析对不同流型条件下诱导管道振动强度进行了分析，揭示了流动参数和流体物性对流致振动的影响规律。本项目研究成果丰富非牛顿流体多相流动规律的理论认识，为井筒和立管多相流理论的发展提供了先进模型、基础数据和基本规律。