Ultrasonic method for measuring water holdup of low velocity and high-water-cut oil-water two-phase flow

Oil reservoirs with low permeability and porosity that are in the middle and late exploitation periods in China＇s onshore oil fields are mostly in the high-water-cut production stage.This stage is associated with severely non-uniform local-velocity flow profiles and dispersed-phase concentration（of oil droplets） in oil-water two-phase flow,which makes it difficult to measure water holdup in oil wells.In this study,we use an ultrasonic method based on a transmission-type sensor in oil-water two-phase flow to measure water holdup in lowvelocity and high water-cut conditions.First,we optimize the excitation frequency of the ultrasonic sensor by calculating the sensitivity of the ultrasonic field using the finite element method for multiphysics coupling.Then we calculate the change trend of sound pressure level attenuation ratio with the increase in oil holdup to verify the feasibility of the employed diameter for the ultrasonic sensor.Based on the results,we then investigate the effects of oildroplet diameter and distribution on the ultrasonic field.To further understand the measurement characteristics of the ultrasonic sensor,we perform a flow loop test on vertical upward oilwater two-phase flow and measure the responses of the optimized ultrasonic sensor.The results show that the ultrasonic sensor yields poor resolution for a dispersed oil slug in water flow（D OS/W flow）,but the resolution is favorable for dispersed oil in water flow（D O/W flow） and very fine dispersed oil in water flow（VFD O/W flow）.This research demonstrates the potential application of a pulsed-transmission ultrasonic method for measuring the fraction of individual components in oil-water two-phase flow with a low mixture velocity and high water cut.

Gas-water stratified flow patterns from electromagnetic tomography

Because of gravitational differentiation of multi-phase fluids, gas-water flow is usually stratified in highly inclined or horizontal gas wells. By using electrode arrays to scan flowing fluids, electromagnetic tomography can identify the flow patterns of mixed fluid from the different electrical properties of gas and water. The responses for different gas-water interface locations were calculated and then physical measurements were undertaken. We compared the results of the numerical simulation with the experimental data, and found that the response characteristics were consistent in the circumstances of uniform physical fields and stratified flows. By analyzing the signal characteristics, it is found that, with the change of the interface location, the response curves showed ＂steps＂ whose position and width were decided by the location of fluid interface. The measurement accuracy of this method depended on the vertical distance between adjacent electrodes. The results showed that computer simulation can simulate the measurement of the electromagnetic tomography accurately, so the physical experiment can be replaced.

A Model for Predicting Holdup and Pressure Drop in Gas- Liquid Stratified Flow

The time-dependent liquid film thickness and pressure drop were measured by using parallel-wire conductance probes and capacitance differential-pressure transducers. Applying the eddy viscosity theory and an appropriate correlation of interfacial sear stress,a new two-dimensional separated model of holdup and pressure drop of turbulent/turbulent gas-liquid stratified flow was presented. Prediction results agreed well with experimental data.

A Model of Turbulent-Laminar Gas-Liquid Stratified Flow

The time-dependent liquid film thickness and pressure drop are measured by using parallel-wire conduc tance probes and capacitance differential-pressure transducer. A mathematical model with iterative procedure to calculate holdup and pressure drop in horizontal and inclined gas-liquid stratified flow is developed. The predictions agree well with over a hundred experimental data in 0.024 and 0.04 m diameter pipelines.

Liquid holdup measurement with double helix capacitance sensor in horizontal oil-water two-phase flow pipes

This paper presents the characteristics of a double helix capacitance sensor for measurement of the liquid holdup in horizontal oil–water two-phase flow. The finite element method is used to calculate the sensitivity field of the sensor in a pipe with 20 mm inner diameter and the effect of sensor geometry on the distribution of sensitivity field is presented. Then, a horizontal oil–water two-phase flow experiment is carried out to measure the response of the double helix capacitance sensor, in which a novel method is proposed to calibrate the liquid holdup based on three pairs of parallel-wire capacitance probes. The performance of the sensor is analyzed in terms of the flow structures detected by mini-conductance array probes.

Characteristics of Salt Water Movement in Iwaki River Estuary, Japan

The present study aims to investigate the characteristics of the motion of salt water and to show the temporal fluctuation of the vertical salinity distribution in Lake Jusan located in the estuary of Iwaki River in Aomori Prefecture, Japan. The Lake Jusan is the best productive water area of the shellfish, corbicula, in Japan in 2013. Then, the lake is very important in Aomori Prefecture as corbicula＇s home. The change of the brackish environment influences the ecology of the corbicula shellfish, then, the shellfish harvest changes every year. Now, it is important to make clear the characteristics of the motion of salt water in the lake. In the present study, observations for the motion of the salt water going up to the lake and going down from the lake to the sea were carried out from June to September in 2015. The present study investigates the time change of the salinity distribution in a perpendicular direction and shows that the movement of the saltwater in the lake can be generated well by the theory given by Sasaki et al., 2009.

基于时域积分的温差流量传感器仿真与试验

目前对于温差流量传感器的研究处于摸索阶段,传感器温度场与流量关系不明确,开展传感器的模拟仿真和试验有助于进一步提高传感器的分辨率和稳定性。为此,通过COMSOL仿真软件对测速传感器温度场进行了仿真分析和试验研究,探究了流量和持水率对测速传感器温度场的影响规律,明确了流量和持水率与时域积分结果的关系。试验结果表明:流量和持水率与积分结果均呈单调递减关系,与仿真结果一致,且在流量0~30 m^(3)/d,持水率0~100%的条件下,测速传感器的分辨率达到了1 m^(3)/d。所得结论可为温差流量检测方法的应用提供理论参考。

低含水油水两相流等效介电常数模型

电容法测油水两相流含水率在油田的地面油水计量及井中的产出剖面分层测试中都得到广泛应用。持水率(水相体积分数)的测量需要建立油水两相流持水率与传感器电容的关系,为此需要建立混相等效介电常数与持水率的理论模型或经验模型。由于油井采出的地层水以及地面实验室标定所用的自来水在低频和中频时均具有良好导电性,因此,单纯考虑介电性而不考虑导电性会对持水率测量的准确性产生显著影响。基于电介质极化的有效电场理论,在低含水且油水状态为精细泡状流条件下,将水视为良导体,建立了油水两相流等效介电常数模型。按此模型,油水两相流的等效介电常数只取决于持水率和油相介电常数,与水相介电常数以及水相电导率无关,初步实验验证了模型正确。该研究对于油为连续相时油水两相流的含水率传感器的设计和现场应用具有重要意义。

基于电导法的油水两相流持水率测量系统设计

针对传统电导法测持水率存在测量电路复杂的问题,设计了一种精简可靠的油水两相流持水率测量系统。该系统使用分压电路检测电导传感器的电压信号,并通过精密全波整流电路将该信号转换成与持水率相关的直流信号,简化了测量电路。同时结合多路复用模块与传感器阵列实现了对持水率的多点检测,提高了检测范围。实验结果表明:该系统的输出电压与持水率之间展现出良好的相关性,当持水率为50%~90%时,灵敏度至少可达0.021 V/%;当持水率为90%~100%时,灵敏度达到最大值0.131 V/%,表明其在高含水状态下持水率检测具有较好的适用性。

油水环状流截面相含率超声衰减法测量

为研究超声衰减法测量油水环状流截面相含率问题,采用COMSOL仿真软件建立油水环状流模型,选择超声传感器结构尺寸6mm和超声发射频率1MHz进行研究,通过分析油水环状流超声衰减特性,确定油水环状流的超声衰减系数与截面含油率关系,并获得线性关系的测量范围。在此基础上进一步研究非理想环状流相关参数对超声衰减特性的影响,并提出将非理想环状流差别阈限用于定量评价非理想环状流因素对于理想环状流超声衰减法的影响,获得非理想环状流差别阈限±10%以内同心度和椭圆度的变化范围。最后开展了油水环状流静态验证实验。研究结果表明:油水环状流截面相含率在5%~30%范围内,与超声衰减系数呈线性关系,同时在此范围内,非理想环状流差别阈限在±10%以内的同心度和椭圆度变化范围分别为0.75~1和0~5%,实验结果和仿真模拟结果具有近似的上升趋势。

高水气比气井井筒压力分布预测方法

东海气田水驱气藏普遍发育,部分气井带水生产,产水井呈现高水气比特征。利用传统两相流井筒压力计算方法进行井筒压力分布预测时,发现目前常用模型存在预测精度较低,影响气井积液状态的诊断及排采措施的选择。为此,通过分析不同井径、不同倾角、不同水气比条件下的气液两相流态,基于Kaya流型判别模型修正得到了适用于高水气比井的流型判别新方法,并对Mukherjee-Brill持液率计算公式相关经验系数进行修正,引入表征水气比的无量纲参数和角度修正系数,建立适用于高水气比气藏的新压降模型。研究表明:新的持液率计算模型对不同管径在不同倾角下的持液率计算误差平均小于15%,新的井筒压降计算方法在东海见水气井井筒压力预测中的精度可提升50%以上,与实测值误差不超过8%。新的井筒压降计算方法对于高水气比气井井筒两相流压力分布预测具有较好的推广应用价值,对水驱气藏开发中后期工作制度优化和排水采气工艺选择具有重要的指导意义。

地面分层注水井口注水量智能控制关键技术

以某石油企业的地面分层注水井口的控制系统为研究对象,开展对地面分层注水井口智能控制关键技术的研究。结合先进传感器,PLC,DTU,PID控制,MODBUS通信协议设计了一套智能控制系统,对该系统的硬件系统、软件系统和远程监控及传输系统进行设计,以此实现对注水量的智能控制并实现各注水参数的远程监控及传输。对在油藏开发应用广泛的超声波流量计传感器安装位置进行优化分析,结果表明:传感器的最小安装高度为传感器所在直管段直径的11倍。提出将PID智能控制策略应用于分层注水,并在地面分层注水井口智能控制系统试验平台上进行智能控制注水试验,确认经过短时间的智能控制后,各层实际流量值均可被调整达到预设值,且误差极小,达到精确控制注水效果。

差压法测量两相流相含率的研究

本文通过差压式测量方法,对气液两相流中含气率及油水两相流中含水率的测量进行了深入的试验研究。通过水平及垂直上升段的结构组合,测量气液两相流中的含气率值,在对流型测量与分析的基础上,建立了不同流型下垂直上升段与水平段摩擦压降间的修正关系式,减小了测量误差;通过采用一缓流的垂直下降段,测量油水两相流中的含水率值,获得了好的结果。

分层注水可调水嘴调节能力仿真计算与分析

注水量精确控制是分层注水工艺的难点,特别是低渗透油藏的小水量分层注水控制尤为困难。根据智能注水井可调水嘴的控制机制,建立了二层分层注水的系统水力学模型。应用有限元方法获得了"U"形可调水嘴的流量系数与水嘴开度的关系,在此基础上数值求解二层注水系统水力学模型,模拟计算了注水量和地层吸水压力变化对水嘴开度的影响。结果表明,注水量和异常的地层压力是制约自动水嘴调节能力的最重要因素,过小的注水量和异常的地层吸水压力会导致水嘴开度过小而无法正常工作。

异重流潜入条件分析及立面二维数值模拟

异重流是自然界中普遍存在的现象，水库泥沙运动中更是经常发生，因此研究异重流的潜入条件有着重要的实践意义。已有很多人对此作了多方面的研究工作。本文对水库异重流的潜入条件进行了理论分析，并用立面二维数学模型作了数值模拟，探讨了影响异重流潜入条件的几个重要因素。

旋流竖井式泄洪洞关键技术问题研究

旋流竖井泄洪洞的关键问题是:(1)涡室进口与竖井连接段跌坎处易产生负压;(2)高尾水位泄洪洞排气难,出口易发生气爆。针对这两个问题,通过试验研究提出消除涡室连接段负压和防止泄洪洞出口气爆的简易工程措施并介绍了涡室、竖井结构尺寸优化研究成果。

大管径水平管油水两相流动特性试验研究

因井斜变化、流体密度差异等因素致使水平井井中流体流动特性复杂多变,准确进行水平井生产动态监测成为难题。基于水平管油水两相模拟试验,在完全水平流、上坡流和下坡流情况下,对油和水的分布规律、流型分类、速度剖面和滑脱效应等进行了分析,通过剖析3种不同持率测量仪器的响应规律,制作了速度剖面和滑脱速度等试验图版,能很好地用于判断流体流动特性。

低液量水平管气液两相分层流压力梯度和持液率研究

低液量气液两相分层流是长距离凝析天然气管线中一种常见流型,文章在大型多相流实验环道上进行了气液两相分层流实验,以动量平衡方程为流动机理分析基础,根据低液量气液两相流动特征,选取双圆环作为界面几何模型;优选气液相间摩擦系数,使低液量气液两相分层流压力梯度计算关系式闭合,计算了低液量分层流的压力梯度和持液率,并将模型预测值与实验实测数据进行了比较分析。在整个实验数据范围内,双圆环界面模型能够很好地预测低液量条件下气液两相分层流的压力梯度和持液率,因此建议在低液量的气液两相分层流中推荐采用双圆环界面模型预测压力梯度和持液率。

低流量三相流动生产测井实验研究

在低流量情况下进行了油气水三相流动模拟实验研究。研究了气流量不同时液流量与含水率、集流流量计响应值、持水率的关系以及气水滑脱速度与持水率的关系。

水电站叠梁门分层取水流动规律及取水效果

对于温度成层型水库,水电站进水口分层取水方式正逐步被采用,目的是尽量取用水库不同层水体,减轻下泄低温水对下游河段环境的负面影响.目前缺乏分层取水流动规律及取水效果的研究.以糯扎渡水电站进水口叠梁门分层取水方案为例,通过数值模拟方法,研究叠梁门分层取水的流动规律,在水库水温分布已知的条件下,探讨叠梁门取水控制下泄水温的效果.研究成果对水电站进水口分层取水设计及运行管理具有重要意义.