A homogeneous model for gas–liquid flow in horizontal wells

Radial influx or outflux stands for the major difference between fluid flow in a pipe and fluid flow in a well. A homogeneous model for gas–liquid flow in a horizontal well is presented in this paper. In addition to frictional and gravitational components of total pressure drop, accelerational pressure drops due to fluid expansion and radial influx or outflux are considered. Effect of radial influx or outflux on wall friction is also taken account for. With a segmented approach, the new model and several existing pipe flow models have been applied to predict pressure drop along a wellbore, and predictions are compared with experimental data. It is found that the new homogeneous model outperforms existing models for gas–liquid flow in horizontal wells.     

表面活性剂对低渗透油藏渗吸的影响

采用不同类型的表面活性剂进行自发渗吸实验,并对表面活性剂改善岩石润湿性、降低界面张力的能力进行了分析。实验结果表明,阴离子型表面活性剂改善润湿性的能力好于其他类型的表面活性剂,且在岩心中的自发渗吸效果最好,这是由于阴离子型表面活性剂改善润湿性的机理为离子对形成机理,强于阳离子的吸附机理;接触角是决定渗吸能否发生的决定性因素,只有接触角小于70°时渗吸才能发生;界面张力影响渗吸速度和最终采出程度,对于渗透率为1 mD的岩心,最佳界面张力为10~(-1) mN/m。     

Transient gas–liquid two-phase flow in pipes with radial influx or efflux

A simplified model for transient gas–liquid flow in pipes with radial influx or efflux has been developed in this paper. The resulting governing equations are essentially hyperbolic with U_tp+c_s and U_tp−c_s as their eigenvalues. A finite-difference scheme based on the split coefficient matrix (SCM) approach is applied to solve the mass and momentum balance equations. Sample numerical simulation runs are performed. Simulation results agree with experimental observations and clearly show the features of variation in pressure drop, liquid holdup, and two-phase velocity during transient and steady state flow periods.     

Effect of drag-reducing polymers on horizontal oil–water flows

The effect of a drag-reducing polymer (DRP) in the water phase during horizontal oil–water flow was investigated in a 14 mm ID acrylic pipe. Oil (5.5 mPa s, 828 kg/m³) and a co-polymer (Magnafloc 1011) of polyacrylamide and sodium acrylate were used. Two polymer concentrations were tested, 20 ppm and 50 ppm, made from a 1000 ppm master solution. The results showed a strong effect of DRP on flow patterns. The presence of DRP extended the region of stratified flow and delayed transition to slug flow. The addition of the polymer clearly damped interfacial waves. Annular flow changed in all cases investigated to stratified or dual continuous flow, while slug flow changed in most cases to stratified flow. In the cases where the slug and bubble flow patterns still appeared after the addition of the polymer, the oil slugs and bubbles were seen to flow closer together than in the flow without the polymer. The DRP caused a decrease in pressure gradient and a maximum drag reduction of about 50% was found when the polymer was introduced into annular flow. The height of the interface and the water hold up increased with DRP. There were no large differences on pressure gradient and hold up between the two DRP concentrations. Using a two-fluid model it was found that the addition of the polymer results in a decrease in both the interfacial and the water wall shear stresses.     

表面活性剂乳化能力差异对低渗油藏提高采收率的影响

表面活性剂驱是低渗透油藏提高采收率的重要技术手段之一,以往筛选活性剂基本以其降低油水界面张力的性能作为评价重点,而表面活性剂的油水乳化性能并未得到足够的重视。为研究油水乳化性能对低渗油藏提高采收率的影响,结合长庆低渗透油藏条件,选用具备相同超低界面张力但乳化能力有所差异的2种活性剂,利用均质、非均质岩心开展驱油实验。实验结果表明:同时具备超低界面张力和强乳化能力的活性剂BA,可在岩心入口段降低渗流阻力,同时实现岩心中部乳化封堵的效果,岩心中部残余阻力系数为2.08;而界面张力超低乳化能力较弱的活性剂TS,无法建立流动阻力,仅起到降压增注的作用。在非均质岩心驱油实验中,水驱后注入BA段塞0.6PV,建立了较高的驱替压力,扩大了波及系数,提高采收率11.46%,而活性剂TS提高采收率幅度为5.88%。     

稠油-水两相水平管流流型实验研究

以高粘度稠油和水为工质,将稠油和水先经搅拌罐混合,再由螺杆泵输送进入实验环道流程,在内径为25.4mm、长52m的水平钢质管道中,模拟了稠油油田现场情况。描述了实验流型,并命名了一种新的流型——Ew/o+D(Ew/o)/w间歇流流型,研究了稠油-水两相管流的压降及反相过程,重点探讨了混合流速对反相的影响。研究结果表明,随着混合流速的增大,反相有提前发生的趋势。在含水率为0.35-0.55时,混合流速的增大将直接引发反相。     

高气液比垂直两相管流流型判别研究

在多相管流中,流型判断准确与否决定着压降计算的精度,根据流型来选择相应的压降计算公式,能提高压降结果的准确性。目前,在现场所遇到的绝大多数多相流问题是气一液(油、气),气一液一液(油、气、水)形式的多相流。本文以气一液两相流为主,着重讨论其流型的划分和判断。并模拟高气液比环境进行了一组室内实验,应用Beggs-Brill、Aziz-Govier、Kaya、Zhmx4种模型分别对室内实验流动形态进行了判断,结果表明Kaya和Zhmx模型对高气液比垂直管流的流型判断比较准确。     

气藏水平井携液临界流量计算

液滴在水平井筒中的受力情况与垂直井筒中截然不同,根据垂直井筒中质点力学分析获得的计算气井携液临界流量的Turner公式及其修正式不再适用于水平井。根据水平井筒内液滴质点分析理论,推导出水平气井的携液临界流量公式。与水平管气液两相流态机理计算得到的携液临界流量结果的对比结果表明,用质点分析理论计算得到的携液临界流量比气液两相流态机理计算结果要偏于乐观,且其流态正处于环状流和雾状流的过渡区。因此,在实际应用中,用质点分析理论计算的结果可根据生产井实际情况在一定范围内进行调整。     

水平井筒气液两相变质量流动流型转变实验研究

在对水平井筒气、液两相变质量流动的流型转变进行了理论研究,在此基础上,设计并建立了流型转变实验装置,对水平井筒气、液两相变质量流动的流型转变进行了模拟实验研究.在轴向为气、液两相流动的前提下分别进行了上管壁单孔眼注入和下管壁单孔眼注入的流型转变实验研究,获得了大量的实验数据.根据实验数据修正了理论计算模型,修正后的理论模型计算结果和实验数据吻合很好.     

The influence of surfactants on the flow characterization of heavy oil

Flow characteristic of oil-in-water emulsion for heavy oil in porous media was studied. A surfactant was screened out and subsequently utilized as the emulsifier in sandpack flooding experiments with different oil-water ratio and permeability. The dual sandpack flooding experiment was conducted to investigate the effect of emulsion in porous media and the ability to enhance oil recovery. Results indicated that the selected surfactant gave a remarkable flow resistance in porous media. Higher oil-water ratio and lower permeability resulted in higher flow resistance. The surfactant increased ultimate recovery of 7.7% by diverting the fluid into low permeability sandpack.     

低产积液气井气举排水井筒流动参数优化

苏里格气田气井具有低压、低产、产水、携液能力差等特点,由于井筒积液严重,部分气井出现压力和产量下降过快的现象,制约了气井的正常生产,因此有必要选择合适的排水采气措施来清除井筒积液。然而,排水采气井筒多相流体流动的机理较复杂,目前,排水采气措施的参数(如气举的注气量)设计多是依靠经验或利用较简单的临界携液流量等参数确定的,针对整个排水采气井筒气液流动规律的变化及能量损失的研究较少。文中通过采用数值模拟和实验模拟研究相结合的方法,对苏里格气田低产积液气井气举前后整个井筒气液流动规律进行分析,并根据注气量对井筒压降和气举效率的影响,确定适用于苏里格气田气井气举复产的最优注气参数,为选择合适的排水采气措施提供了理论指导。     

搅拌测量法测定油水混合液流动特性

对于非均匀混合(乳化)、不稳定的油水两相体系,传统的黏度计无法测量其黏度。通过搅拌可以维持油水两相的均匀混合状态,并且搅拌轴的扭矩反映了流体的当量黏度。基于这一原理,建立了搅拌测量油水混合液流动性的方法,包括搅拌桨叶类型的选择、根据搅拌轴扭矩确定一定搅拌转速下的黏度、根据搅拌转速及流体黏度确定搅拌槽的平均剪切率。针对单相原油和油水混合液,将该方法的测量结果分别与同轴圆筒黏度计和试验环道的测试结果进行了对比,验证了其可靠性。应用该方法,对高含水油水混合液在不同温度和含水率条件下的流动性进行了测量,结果具有良好的规律性。     

油气水混输减阻理论与方法

基于新滩垦东 18油水采出液的乳化水含量及特性 ,分析油气水在混输过程中的流动状态。应用反相乳化降黏法和气 非牛顿流体流动规律 ,研究W /O型乳状液的降黏效果、油水混输减阻效果以及油气水混输减阻途径。结果表明 :①油气水在混输过程中容易形成呈非牛顿特性的W /O型乳状液 ,油气水混输问题可归结为气液两相流中的气 非牛顿流体流动问题 ,其水力计算可参照成熟的气液两相流动的相关处理方法 ;②采用适当的降黏剂 ,可以有效地降低W /O型乳状液的黏度和油水混输压降 ,降黏率可达到 99%以上 ,减阻率可高于 6 0 % ;③油气水混输减阻可通过采用适当的化学剂改变W /O型乳状液的内外相或阻止其形成实现 ,其关键在于降低W /O型乳状液的稠度系数和流性指数或油水界面张力。     

气—幂律两相流体流经截面突缩管的数值模拟

为揭示空气-幂律流体流经截面突变时的两相流动规律,尤其是两相参数沿流向及管截面分布及压降的变化规律,根据气液两相流理论,并考虑幂律流体的本构方程,建立了空气-幂律流体两相流动数学模型。在此基础上,采用商业软件Fluent对空气-幂律两相混合物流经截面突缩管道的流动特性进行了数值模拟,获得了两相参数沿轴向及截面方向的分布规律。研究表明:气相、液相速度及压降随着输入含气量的增大而增大;两相参数在截面突变附近有急剧的改变,但其突变位置却有所不同;另外,两相参数的截面分布沿流程也有所不同。这些研究结果对相关系统的设计提供了理论依据。     

基于实验研究的油气钻采水平两相流管道泄漏声发射检测

气液两相流管道在油气钻采、运输中应用广泛,但对其泄漏检测的研究较少.本文通过搭建水平气液两相流泄漏实验系统,利用声发射(AE)检测原理对气体压力、流型、泄漏孔径、泄漏位置等因素对泄漏声发射信号的影响进行了实验研究,提出通过经验模态分解(EMD)去噪并用小波包分解(WPD)提取声发射信号特征输入BP神经网络进行泄漏存在性...     

Numerical study of dispersed oil–water turbulent flow in horizontal tube

In this paper, the three-dimensional flow of two immiscible liquids in a horizontal pipe has been investigated numerically. The transient numerical simulations of two-phase dispersed flow in a pipe (of ID = 0.0024 m) have been carried out using commercial CFD package FLUENT 6.2 in conjunction with multiphase model. Oil–water system is selected as the two-phase system in this work. The k − ε model was used to describe the turbulence in continuous phase. The numerical results in terms of the phase distribution profiles and average in-situ hold-up are presented and discussed. The predicted results are seen to be in good agreement qualitatively as well as quantitatively with the previous experimental results available in the literature.     

不同曳力模型对提升管内气固流动特性的影响

在考虑稠密气固两相流中颗粒具有非均匀流动特性的情况下,提出了基于颗粒团聚效应的气固相间曳力模型,数值模拟循环流化床提升管内气固两相的流动特性。模拟计算时考虑气固相间的作用力,壁面处气相采用无滑移边界条件,固相采用考虑颗粒与壁面的碰撞和颗粒与壁面的简单摩擦作用的壁面边界条件。结果表明,考虑颗粒团聚效应的曳力模型能很好地反映提升管内气固两相流动特性,模拟结果比应用Gidaspow曳力模型的计算结果更接近文献[16]的试验结果。     

封头对板翅式换热器流动及阻力特性的影响

研究了不同Re下3种封头结构对板翅式换热器内部物流分配和阻力分布特性的影响。实验结果表明工业用基本型封头造成板翅式换热器内部物流分配极不均匀,而孔板型封头结构能有效地降低不均匀参数和最大流速比,可极大地改善物流分配的效果,并且随着Re的增大效果越明显;还发现物流分配的不均匀性会导致流动阻力分布更加不均匀。综合研究分析可得封头结构和Re是影响板翅式换热器物流分配和阻力分布特性的重要因素,而错排孔板型封头结构的改善效果最佳。     

Linear stability analysis and experimental verification of stratified air–water flow in a horizontal bend

Stratified flow in gas–liquid systems is a basic flow configuration which occurs frequently in industries due to the large density differential between the phases that helps to sustain stable stratification for relatively wide ranges of flow rates. The study on stability of stratified flow and the development of transitional criteria to various flow patterns have been very actively pursued for straight pipes, resulting in a broad understanding of the underlying mechanisms. Beside straight pipes, pipelines contain other fittings, which pose abrupt changes to the flow direction, and hence their impact on the flow stability needs to be ascertained.This study attempts to extend the linear stability analysis of stratified flows in a straight pipe to a horizontal bend. A model for the effect of a horizontal elbow on the transition from stratified to non-stratified patterns using the two-fluid approach is presented. The Inviscid Kelvin–Helmholtz (IKH) and Viscous Kelvin–Helmholtz (VKH) stability criteria for stratified flow transition are derived.Experiments are carried out using air and water in a 0.05 m diameter horizontal pipe work containing an intermediate bend of 0.5 m radius of curvature and the flow pattern observed in the bend is compared with the stability theory. The results show that the IKH and VKH stability criteria for stratified flow in a bend have identical forms as their counterparts in an inclined straight pipe, except that the tilt of the liquid lump in the bend which depends on the liquid velocity replaces the inclination angle for a straight pipe. The stable region is over-predicted by the IKH criterion while the VKH criterion shows good agreement for transition from stratified to slug flow if the liquid surface gradient is taken into account in the solution of the flow parameters under fully developed conditions.The work presented in this paper is of tremendous help to oil production engineers who need to know and control the flow regime transitions in order to avoid problems associated during production. These problems are mainly due to the generation of slug flow which leads to severe unwanted jigging.