倾斜管内高黏油水两相流的数值模拟

采用Fluent三维数值模拟方法研究了倾斜管内高黏油水乳化前后的流动状态,从流型与压降两方面总结了油水两相流的流动规律。实验结果表明,乳化前油水两相流的流型呈现油水交替、泡状流、水塞流、弹状流和环状流,而乳化后则以分层流、分散流、分层流且带有水包油为主。在一定倾角和入口流速下,管内压降随含水率的增加急剧减小;在一定入口流速和含水率下,管内压降随倾角增加逐渐减小。正交实验结果表明,入口流速对压降的影响最大,含水率次之,倾角的影响最小;最优组合为倾角20°、入口流速0.4 m/s、含水率40%。     

水平圆管油水两相变质量分层流压降计算

以往对水平圆管中复杂流体介质的流动规律研究的对象均是对水平圆管单相和气液两相变质量流动,关于存在壁面入流条件的水平圆管油水两相变质量流动的研究较少。为此对水平圆管油水两相变质量分层流动进行了微元分析,考虑壁面入流对其中油水两相变质量分层流动压降的影响,分别对油水两相应用连续性方程和动量守恒方程,得出了水平圆管油水两相变质量分层流动的基本模型和压降计算模型。通过模型求解揭示了在壁面入流条件下沿水平圆管的压降规律,并分析了壁面入流、圆管直径、油相黏度和含水率等主要参数对其中压降规律的影响。计算结果表明,当油相黏度较大时,随含水率的增加,沿水平圆管压降降低;而油相黏度较小时,随含水率的增加,沿水平圆管压降升高。     

水平直管中气液两相分层流动压降的实验研究

为了探索气液两相流流动参数变化对水平圆管中气液两相分层流动压降的影响及压降的计算方法,在天津大学双闭环中压湿气实验装置上开展了实验。实验工况为:压力为0.2~0.8 MPa,气相表观流速为6~12 m/s,质量含水率为0~79.6%,管道直径为50 mm,实验压降测量长度为3 m。实验结果表明,压力、气相流速、质量含水率等参数都会影响水平圆管两相流动压降的大小,其中含水率是影响压降的关键因素。选择经典的Chisholm模型和考虑相界面形状对两相摩擦系数影响的ARS模型进行压降预测,预测结果:平均误差分别为25.89%和11.56%,不确定度分别为29.44%和11.88%。进一步分析截面含气率与摩擦系数对Chisholm模型压降计算值的影响,得知摩擦系数是其中主要的影响因素。将两相摩擦系数与单相摩擦系数的比值引入Chisholm模型对其进行修正,修正之后的Chisholm模型压降计算值平均误差为11.27%,不确定度为14.66%。     

垂直同心环空管内上升油水流动实验

以水和机械油为工质对垂直同心环空管内上升油水两相流动进行了研究，根据实验得到了油水两相流动的流型分布。在实验的基础上，通过一定的理论分析得到了各种流型的转换准则，对油水流动的持油率，压降的预测及相转变点的压降特性也进行了一定的研究，这些研究结果对环形管道油井的参数预测（如含水率，压降等）有一定的参考价值。     

含有油水乳状液油气水三相分层流的水力学模型

在油气水的三相管内流动中,分层流同样也是一种常见流型。由于互不相溶的油水两相之间相互作用及分散程度的复杂性,所以油气水三相分层流比一般的气液两相分层流要复杂许多。使用一维三流体模型求解含有油水乳状液的分层流、即气体/(W/O型)乳状液/(W/O/W型)多重乳状液的三相分层流。通过模型的求解可以确定油气水分层流的相分率及其他相关参数和压降。     

油水两相管流测量方法应用进展

随着科学技术的发展,大量基于电学及光学基础的测量设备逐渐被学者们用于定量描述油水两相流动规律的研究中。通过简述国内外关于油水两相管流实验中所采用的测量方法及测量原理,总结电导探针、聚焦光束反射测量仪、光学测量设备及伽玛相分率仪在油水两相管流动中的应用进展,并在其基础上分析了各种测量方法的局限性。根据管流油水流动研究现状,提出油水两相管流研究应从两相流场信息测量及油水界面捕捉入手,通过实验确定影响油水两相相间作用的决定性因素,建立新的流型转化机理,明确局部及完全分散对有效黏度变化的影响趋势,并结合现有两相流动规律,改进及完善了现有压降计算模型。     

地面驱动螺杆泵泵送油水乳化液时的摩阻研究

对地面驱动螺杆泵泵送油水乳化液时的摩阻特性进行了全面的研究。通过测量摩擦压降研究了油包水与水包油乳化液之间的相转变现象,分析了不同含水率下抽油杆转速对油包水乳化液及水包油乳化液流动摩擦压降的影响。实验和分析表明,当含水率为0.41~0.43时,水包油乳化液将向油包水乳化液转换;抽油杆的旋转效应在水包油乳化液时对摩擦压降的影响要大于油包水乳化液。通过实验数据处理,获得了不同流型下抽油杆旋转时环型管道内幂律型油水乳化液流动摩擦阻力的实验关系式。这些研究结果对地面驱动螺杆泵的设计及应用有一定参考价值。     

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蛇曲井是不同于常规水平井的一种新型复杂结构井，其水平段在纵向上存在较大起伏，不能用常规水平井的压降模型计算其压降。文章对蛇曲井微元段的两相分层流动进行了分析，根据连续性方程和动量方程, 建立了蛇曲井水平段两相分层流动的压力梯度模型，在定产量和定井底流压两种工作制度下，给出了蛇曲井的水平段在两相分层流时的压降计算方法。应用文章所建模型和水平井的水平段压降计算模型分别计算了某蛇曲井水平段在气水两相分层流动时的压降，结果表明蛇曲井水平段的井筒压降不能用常规水平井水平段的压降模型计算，蛇曲井水平段的井筒压降不能忽略。     

水平井的层流新模型

本文给出了水平井中油水两相层流的物理模型，并应用流动环路实验数据建立了一种新的界面摩擦系数相关关系。     

水平井筒变质量气液两相流动模型

根据水平井筒和常规水平管道中气液两相流动的相似和差别,可知常规水平管流的流型转换标准用于井筒流动需要进行修正或扩展。根据气液两相界面波的迅速成长机理,考虑了管壁存在入流或出流对于分层流向非分层流流型转变的影响,在Taitel Dukler的研究基础上,得到水平井筒气液两相变质量流动分层流向非分层流流型转变的判别方法。通过对分散泡状流流型中的分散气泡进行受力分析,考虑了管壁入流或出流的影响,得到判别水平井筒气液两相变质量流动分散流向间歇流流型转变的一种新方法。     

A united model for predicting pressure wave speeds in oil and gas two-phase pipeflows

A pressure wave, caused by unsteady operations such as a shutdown or restart, pigging, slug flow or input flow rate transient changes during an oil–gas pipeline transmission, could cause a safety hazard to the whole pipeline system. Because of the compressibility of the gas phase, the changes of interface between the gas and liquid, the momentum and energy transfer between the two-phase and the single-phase to the wall, all make it complicated for predicting the pressure wave speeds for oil and gas two-phase flow in long-distance pipelines. On the basis of the gas–liquid two-fluid model, this paper analyzes the pressure wave propagation for the two-phase flow. Pressure sources of gas–liquid momentum equations are described as the function of the gas–liquid flow velocities, gas void fraction, void fraction gradient and their differentiations, which make the two-fluid model hyperbolic. With the introduction of virtual mass force, the united model for prediction of the pressure wave speeds has been developed. And the gas–liquid Equations of State (EOS) has also been used in the united model, which can analyze the effects of the different system pressures. Important factors, such as the virtual mass coefficient and the gas void fraction, are also discussed. The developed model fits well with the experimental data, and can be used to predict wave speeds for different flow patterns, such as stratified flow, dispersed bubble flow and slug flow.     

Effect of binary mixtures of surfactants on horizontal gas–liquid flow with low liquid loading

The interaction between anionic and zwitterionic surfactant (sodium dodecyl sulphate/dodecyl betaine) brings about the synergism in the surface tension reduction and the micelle formation. The binary mixtures of surfactants were added to air–water flow with low liquid loading in a horizontal 50.8 mm pipe. Two concentrations with a 6:4 molar ratio of zwitterionic to anionic surfactant were tested to investigate their effect on the frictional pressure drop. Parallel ring conductance technique was used to trace the liquid layer fluctuation near the pipe wall and examine the gas–liquid interfacial behavior. A modified two-fluid model with the consideration of a curved interface is introduced to obtain the closure relationship for scaling the gas–liquid interfacial roughness. It was found that the solution with low concentration did not have drag-reducing effect although the reduced surface tension, while the mixed surfactants solution with the concentration higher than the critical micelle concentration reduced the interfacial roughness, leading to pressure drop reduction at low and medium gas flow rates. At high gas flow rates, the effect of mixed surfactants became worse because of the degraded surface activity and the break-up of the mixed micelle under the high gas shear conditions.     

Numerical Study of Stratified Gas-Liquid Flow

In this work the effects of empirical correlations of friction factors (wall and interfacial) on the numerical stability and parameters predictions in stratified gas-liquid pipelines flow, was studied using the two-fluid model, where unequal phase pressure effects were considered. To study the effects of such empirical correlations without taking into account the instabilities due to ill-posed initial-value problems or multiple solutions, the two-fluid model was solved using input data, which satisfies a linear stability criterion where multiple solutions do not occur. In general, we found that the empirical correlations are not important for numerical stability but do, however, affect significantly the parameters predictions.     

Numerical Study of Stratified Gas-Liquid Flow

Abstract

In this work the effects of empirical correlations of friction factors (wall and interfacial) on the numerical stability and parameters predictions in stratified gas-liquid pipelines flow, was studied using the two-fluid model, where unequal phase pressure effects were considered. To study the effects of such empirical correlations without taking into account the instabilities due to ill-posed initial-value problems or multiple solutions, the two-fluid model was solved using input data, which satisfies a linear stability criterion where multiple solutions do not occur. In general, we found that the empirical correlations are not important for numerical stability but do, however, affect significantly the parameters predictions.     

Transition Model of Stratified Oil-water Flow in a Horizontal Pipe

In this article, transition between stratified and nonstratified horizontal oil-water flows is modeled with three-layer model which is originally developed for gas-oil-water flow, and modified three-layer model is applied for the determination critical wave amplitude, which becomes unstable in stratified flow. The results are seen to be in agreement with experimental data available in the literature.     

胶凝原油管道恒流量启动过程中的启动波速

胶凝原油管道在恒流量启动的过程中同时存在着启动波速和水击波速,其中启动波速是主导管道再启动时压力推进过程的关键因素,对管道启动压力的计算有直接影响。在阐述启动波速与水击波速之间区别的基础上,推导出了胶凝原油管道恒流量启动波速的数值计算公式,并通过管流实验验证了其可靠性。在胶凝原油管道恒流量启动过程中,启动波速明显小于水击波速,且随着传播距离或传播时间的增长而呈衰减规律,但由于衰减速率会逐渐降低,因而启动波速有趋于稳定的趋势。此外,启动波速还随胶凝结构强度的增加而减小,随启动流量和凝油体积弹性系数的增加而增加。     

用密度波特征波速判定环空多相流流型的转变

钻井环空多相流流型判定目前主要依靠经验公式,存在着一定的误差。为此,考虑钻井液相湍动、脉动速度、虚拟质量力、斯托克斯力、相界面动量传递等因素,在双流体模型的基础上,建立了密度波特征波速判定环空多相流流型转变的模型,并利用小扰动线性法,通过编程计算求解。研究结果表明:(1)由所建模型计算的数据与前人密度波不稳定判断流型结果一致;(2)虚拟质量力对密度波特征波速判断流型的影响较大,随虚拟质量力系数增大,泡状流向弹状流转变的空隙率增大;(3)随井深增加,分散气相密度增大、气相与钻井液相相对密度增大、界面膜稳定性增强,分散气相液滴不易发生聚集,泡状流向弹状流转变空隙率增大;(4)密度波一次不稳定性导致分散气相从泡状流聚合为弹状流,密度波二次不稳定现象导致气相继续聚合,逐渐形成连续的气体环状,从而发生弹状流向环状流转变,密度波的二次不稳定现象多发生在井口环空段。结论认为,利用密度波特征波速来判定井筒流型转变是可行的。     

减阻技术对海洋油气管线中多相流动与传热的影响

在海洋环境中多相流条件下应用减阻技术,可以在相同的管线压力下,有效提高油气输送量。减阻技术影响多相流的摩擦阻力、持液率和界面现象,可使多相流的的减阻率最高达到60%以上,可减少多相流体与管壁间的传热;某些情况下,减阻技术还能够改变多相流的流型、抑制剧烈弹状流,改善油气输送系统的运行工况。     

钻柱偏心旋转对环空摩阻压降影响的数值模拟研究

准确预测钻柱偏心旋转工况下的环空摩阻压降是复杂结构井控压钻井的重要理论基础,但常规钻井液环空摩阻压降计算方法无法直接计算复杂结构井的环空摩阻压降。为此,应用数值模拟方法,分析了偏心度（0～67.42%）和钻柱转速(0～114.65 r/min)对典型环空（Ф127.0 mm钻杆和Ф215.9 mm井眼）中摩阻压降梯度的影响。分析结果表明：偏心度小于45.00%时,转速和偏心度对摩阻压降梯度影响较弱,摩阻压降梯度随转速增大略有降低,随偏心度增大而增大;偏心度大于45.00%时,低转速（<60 r/min）下摩阻压降梯度随偏心度增大而降低,高转速（≥60 r/min）下摩阻压降梯度随偏心度增大而略有增大。基于数值模拟结果,建立了偏心度分类的无因次偏心环空摩阻压降梯度预测模型,计算了南海某水平井Ф215.9 mm井段的ECD,并与PWD测试结果进行了对比,平均相对误差为0.45%,表明该模型具有较好的准确性。研究结果表明,无因次偏心旋转环空摩阻压降计算模型可以精细描述环空压力场和准确计算ECD,为控压钻井水力参数优化提供指导。