连续管幂律流体流动及压降影响因素分析

幂律流体是石油工程领域应用非常广泛的非牛顿流体,为了研究其在连续管螺旋管段的复杂流动状况和压降变化,基于Fluent软件模拟了幂律流体在螺旋管内的流动,分析了管径、滚筒直径、入口速度、流体密度、流体稠度系数以及幂律指数对压降的影响,得到了截面上的压力和速度分布,总结出了螺旋管压降随各个参数的变化规律:在直管段截面压力和速度呈同心圆状规则分布,而在螺旋管截面压力和速度则向外凹陷;螺旋管的湍流核心区较直管段减小,说明曲率增大导致黏性力的作用范围变大;油管压降随入口速度、流体密度、稠度系数和幂律指数的增大而增大,其中幂律指数的影响比稠度系数大得多;压降随管径的增大而减小,滚筒对压降的影响可以忽略;当流速很高时,为了减小压力损失,保证平稳流动,应在保证所需井下压力的基础上选择管径稍大的油管。研究结果可为现场确定连续管和流体的相关参数提供理论指导。

Power-Law Fluid Flow in Coiled Tubing and Pressure Drop Influence Factors Analysis

Power-law fluids are non-Newtonian fluids that are widely used in the field of petroleum engineering. To study the complex flow conditions and pressure drop changes in spiral sections of coiled tubing,the flow of power-law fluids in spiral tubing was simulated based on Fluent software. The effects of tubing diameter,roller diameter,inlet speed,fluid density,fluid consistency coefficient,and power law index on pressure drop were obtained. The pressure and velocity distribution on the cross section were obtained. The law of pressure drop of the spiral tubing with each parameter was summarized: in the straight section,the pressure and velocity are regularly distributed in concentric circles. But the pressure and velocity in the spiral section are recessed outwards. The turbulent core area of the spiral section is smaller than that of the straight section,indicating that the increase in curvature leads to the increase of the range of viscous force. The pressure drop in the coiled tubing increases with the inlet velocity,fluid density,consistency coefficient,and power law index. The influence of the power law index is much greater than the consistency coefficient. The pressure drop decreases with the tubing diameter. The effect of the roller on the pressure drop can be ignored. When the flow rate is high,to reduce the pressure loss and ensure smooth flow,larger diameter tubing should be selected on the promise of required downhole pressure. The study results can provide theoretical guidance for determining the relevant parameters of coiled tubing and fluids.