SOLUTION NONUNIQUENESS FOR SEPARATED GAS-LIQUID FLOW IN PIPES AND WELLS. I. OCCURRENCE

The occurrence of multiple solutions has been investigated and discussed in this paper. Multiple solution regions are displayed by either a U_SL-U_SG map or a X-Y map. It is found that many parameters impose influence on the multiple solution regions, including fluid properties, pipe ID, pipe inclination angle, wall inflow or outflow, empirical correlations for wall friction and interfacial friction factors, and so on. For example, the multiple solution region could change significantly if different interfacial friction factor correlations are applied. Multiple solutions are only possible for upward flow for separated flow in a pipe without wall mass transfer. However, for wellbore flow case, depending on wall inflow or outflow of fluids and their flow rates, multiple solutions may also exist for horizontal and downward flow. More specifically, for wall inflow case (production well), multiple solutions only exist for upward flow for the gas inflow-dominant case, whereas they may exist for upward, horizontal and downward flow for liquid inflow-dominant situations. The opposite is expected for wall outflow (injection well) case.     

SOLUTION NONUNIQUENESS FOR SEPARATED GAS–LIQUID FLOW IN PIPES AND WELLS. II. ANALYSIS

ABSTRACT

As shown in [10] Ouyang, L.-B. and Aziz, K. 2001. Solution Nonuniqueness for Separated Gas–Liquid Flow in Pipes and Wells – Part 1: Occurrence. Petroleum Science and Technology, in press [Google Scholar], multiple solutions may occur for upward flow for separated flow in a pipe without wall mass transfer. For the wellbore flow with wall inflow (production well) case, multiple solutions only exist for upward flow for the gas inflow-dominant case, whereas they may exist for upward, horizontal and downward flow for liquid inflow-dominant situations. The opposite is expected for the wall outflow (injection well) case. The transient models have been proposed for separated (stratified and annular-mist) gas–liquid flow in pipes or wells and successfully applied to validate, both physically and numerically, the correct solution of liquid holdup and pressure drop whenever multiple solutions exist for separated flow. Physical considerations and numerical simulation have shown that only the solution with the lowest liquid height (holdup) is physically realistic. The solutions corresponding to the intermediate and the highest liquid holdup may not be able to lead to a stable flow.     

A mechanistic model of heat transfer for gas–liquid flow in vertical wellbore annuli

The most prominent aspect of multiphase flow is the variation in the physical distribution of the phases in the flow conduit known as the flow pattern. Several different flow patterns can exist under different flow conditions which have significant effects on liquid holdup, pressure gradient and heat transfer. Gas–liquid two-phase flow in an annulus can be found in a variety of practical situations. In high rate oil and gas production, it may be beneficial to flow fluids vertically through the annulus configuration between well tubing and casing. The flow patterns in annuli are different from pipe flow. There are both casing and tubing liquid films in slug flow and annular flow in the annulus. Multiphase heat transfer depends on the hydrodynamic behavior of the flow. There are very limited research results that can be found in the open literature for multiphase heat transfer in wellbore annuli. A mechanistic model of multiphase heat transfer is developed for different flow patterns of upward gas–liquid flow in vertical annuli. The required local flow parameters are predicted by use of the hydraulic model of steady-state multiphase flow in wellbore annuli recently developed by Yin et al. The modified heat-transfer model for single gas or liquid flow is verified by comparison with Manabe's experimental results. For different flow patterns, it is compared with modified unified Zhang et al. model based on representative diameters.     

Liquid holdup in horizontal two-phase gas—liquid flow

The purpose of this study was to simplify and improve the mechanistic model developed by Taitel and Dukler (1976) for estimating the liquid holdup in horizontal two-phase flow. An experimental study was first conducted to develop a data bank used for evaluation and improvement. The holdup data were obtained using an air-kerosene mixture flowed through a test section consisting of a horizontal pipe 2-in (50.8 mm) in diameter and 118 ft (36 m) long. The liquid holdup ranged from 0.009 to 0.61 and the flow patterns observed were stratified, slug and annular.It was shown that the Taitel-Dukler model, which consists of several equations and requires an iterative method to solve, can be accurately represented by a single explicit equation.Based on the measured data, it was found that Taitel-Dukler model tends to overestimate liquid holdup for stratified wavy, slug and annular flow patterns, whereas it tends to underestimate the liquid holdup for stratified smooth flow. An empirical modification, therefore, is proposed which results in a significant improvement in predictions compared to experimental data.Based on statistical results, it is observed that the proposed model gives excellent results and clearly outperforms the original model and all the existing correlations when tested against the present data (89 points) and against data from the literature (111 points).     

多相管流中压降和持液率的影响因素分析

在多相管流中,影响压降的主要因素有温度、管径、管路粗糙度、气液相流量等,影响持液率的因素主 要有压力、管径、气液相流量等。针对高粘原油用不同的计算模型,编制了压降和持液率的软件进行了计 算,并结合具体的算例对压降和持液率的影响因素进行了分析。     

连续测量全井眼过环空产出剖面测井仪

介绍了连续测量全井眼过环空产出剖面测井仪器的结构和工作原理，并对其在室内实验及现场测井资料进行了分析。仪器由全井眼持水率传感器、集流型涡轮流量计和集流扶正器构成。持水率传感器由测量、校正两部分构成。传感器最终输出仅由油水两相流持水率决定，实现了持水率的全井眼测量。仪器配接了1个带有扶正器的集流器，在实现连续测量扶正的同时，进行半集流方式的流量测量。现场测井时，流量和含水率测量值均采用随不同深度连续测量方式。所测流量的曲线可直观反映出井内各产层的产液情况，连续持水率曲线可以直观反映出各产层的持水率变化情况，结合井口化验结果就可以对1口井的各层位的产水和产油情况作基本判断，提供直观的解释结果。     

光纤探针持气率计模拟井实验数据分析

根据光纤探针对气液界面反射率不同的特点设计了光纤探针持气率计,用于生产井持气率的测试。为了证明持气率测量的可行性,用试验仪器分别在气水两相流和油气水三相流中做了持气率试验。文章研究了光纤探针持气率检测,并对检测数据进行了比较分析,总结出仪器试验的特点,为光纤探针持气率测量提供了有力的依据。     

在水平井中应用的一种新型多相持率测井仪--电容阵列多相持率测井仪(CAT)

新型的多相持率测井仪(电容阵列多相持率测井仪(CAT))采用许多传感器分布在套管内壁附近，或分布在不同半径的圆周上，在井中相同深度测量各相持率。仪器的传感器采用微型的电容传感器探测周围流体的电导率。对于油、气或水．电容传感器的电路输出三种不同的频率来测量三相持率。目前，该仪器已成琦应用于塔里木盆地的水平井测试作业中。     

煤层气集输管道持液率影响因素及排液点优选

煤层气开采压力低、产量小,且常含有大量液态水,集输管道上坡段容易产生管道积液,使得摩阻增大并出现段塞流,引起压力骤降,不利于集输管道安全运行。本文利用模拟软件OLGA分析入口流量、管径、气液比和出口压力对煤层气集输管道持液率的影响,得到了煤层气集输管道各管段持液率分布规律,并进一步比较了基于管道持液率、流型、压降和排液点个数的4种排液点设置方案。结果表明,煤层气集输管道压力骤降段均出现在上坡段,出口压力对管道持液率影响最为显著,入口流量和气液比对管道持液率影响规律相似,不同管径下管道持液率在流动方向上的分布也具有一定的相似性;设置排液点后,管道持液率明显下降,管道积液情况得到改善,且方案比较表明,当排液点设置在管段低洼处时,管道持液率最低,且各管段均无段塞流出现,管道压降最小。     

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凝析气相是多元组分的气体混合物，以饱和烃组分为主，在输送过程中由于沿线温度、压力的变化引起的凝析和反凝析现象显著，这使凝析气的管道输送不同于气体或液体的单相输送，其管输方式可分为气液混输、气液分输。气液两相混输投资少、工期短，但要解决困凝析液的积聚而降低输送能力及液塞处置等技术问题；气液分输是先将凝析气分离，然后将天然气和凝析液分别输送，管内流体均为单相流动，气液分输又可分为双管输送和顺序输送。凝析气的气液混相输送是多相流输送的一种特例。针对东海平湖油气田海底输气管道采用多相流技术输送凝析气的实例，分析了凝析气混相输送管道压降、输量和持液率的关系，并指出了预测管路温度下降值是管路安全运行的必要条件。通过对平湖凝析气管道的运行分析，强调工艺配套是多相流技术成功应用的重要条件。     

严重段塞流压力及持液率波动特性试验分析

利用中国石油大学(华东)自主设计的试验装置,对严重段塞流的压力及持液率波动特性进行了初步研究。在相同工况下,严重段塞流的发生范围随着管道下倾角的增大而稍微增大;严重段塞流的发生严格受到气、液相流量大小的限制,只有在气、液两相流量都较小的工况下,严重段塞流才会发生;稳定流态(即试验数据采集过程中气、液相流量保持恒定不变的状态)下,严重段塞流的压力及持液率波动呈周期性变化,压力波动幅度是未发生严重段塞流现象时的数倍,持液率波动幅度也明显比未发生严重段塞流现象时大。     

A condensation model for calculating pressure gradients in condensate wells

A method is presented to calculate pressure traverses in a condensate well utilizing existing techniques for two-phase flow of fluids in pipes. Existing correlations have been developed for black oil flow where gas evolves from the oil as pressure and temperature are reduced. In the case of condensate flow, a liquid evolves as pressure and temperature are reduced, thereby making the existing correlations inapplicable. The Peng-Robinson equation of state is used to model the gas/condensate fluid and predict the gas/liquid ratio at any pressure and temperature as a traverse is calculated for the depth of the flowing well. The existing two-phase flow correlations for black oil flow are used in this work to predict gas/liquid properties such as liquid holdup, friction factors, and flow regimes. This model is then applied to several wells for which extensive data was taken, including PVT properties and pressure measurements.     

水平井、斜井集流式生产测井实验研究

低产液井、斜井、水平井生产动态监测是生产测井领域的难题.斜井、水平井多相流动实验结果表明,不同井斜情况下集流伞的流量频率值均随着液流量的增大而增大;完全水平状态下流量频率值受含水百分比的影响较大,同等流量情况下随着液体中含水百分比的增大先逐渐减小,而后逐渐增大;在井斜或垂直状态下,流量频率值受含水百分比的影响较小,当液流量较大时,流量频率值与液流量呈较好的线性关系;当液流量较小时,随着井斜角的增大,对集流流量计和持水率计的影响会逐渐增加,相比较而言,对持水率计的影响更为严重.井身达到水平时,采用持水率资料计算含水率时误差较大.     

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。     

页岩气水平井井筒积液流动规律研究——以C01井区为例

目的 C01井区页岩气井开采中后期,天然能量不足,井筒积液普遍,准确实时识别积液位置困难,导致排水采气工艺实施效果欠佳,故需针对井筒积液流动进行研究。方法 基于C01井区积液现状,在Beggs持液率模型的基础上,使用生产数据及井筒流型对持液率模型进行修正,从而可以准确地实时识别积液位置,与生产测井剖面实测数据进行对比,验证了修正模型的准确性;基于实际页岩气井钻井数据建立了页岩气井的全井段几何模型,实现了气液两相流动模拟,分析了井型对积液位置的影响。结果 修正的持液率模型在页岩气井中应用时,其平均相对误差为6.66%,可以为现场提供较为准确的积液位置识别;数值模拟结果表明,下倾型和上倾型页岩气水平井由于能量衰减导致造斜段易形成积液。结论 应用修正的持液率模型计算积液位置显示,页岩气水平井造斜段易形成积液;数值模拟结果与修正的持液率模型应用计算结果符合,通过使用预测的生产数据可以对井筒积液位置进行预判。     

KINETIC RATE EXPRESSION FOR METHANOL SYNTHESIS IN A LIQUID ENTRAINED REACTOR

In the three phase entrained reactor for the liquid phase synthesis of methanol, the catalyst-inert oil slurry is pumped through the tubular reactor and syngas is fed to the reactor cocurrently with the upward flow of slurry.

According to an elaborate experimental design plan, the effect of different operating conditions on the liquid phase synthesis of methanol in an entrained reactor, was studied. The parameters of this experimental study included reactor temperature, reactor pressure, slurry flow rate, syngas flow rate, slurry holdup tank pressure, and syngas composition.

The data obtained from the experiments at low catalyst loading in slurry, were used to develop a kinetic rate expression for the liquid phase methanol synthesis process in an entrained reactor. This in turn helps the scale-up and commercialization of the methanol synthesis process in an entrained reactor.     

水平井生产测井技术应用

通过技术合作，对水平井生产动态监测测井技术进行了探索，取得了一定效果。介绍了水平井产出剖面测井的关键技术。介绍了将测井仪器送入水平钻穿的地层中的3个传输测井工艺，包括钻杆传输方法、柔性管传输方法和井下牵引输送方法；介绍了所采用的测井系列，重点分析解决油汽水三相分离问题的测井方案；介绍了水平井测井资料的解释和评价技术；通过模拟实验，确定井中4种流体流型，提出持液率关系式和流量测井响应关系式。     

流体物性对悬浮床加氢环流反应器的影响

利用计算流体力学方法采用标准k-ε湍流模型和欧拉两相流模型对重油悬浮床加氢环流反应器进行数值模拟,考察了气相密度、液相密度、液相黏度等流体物性对环流反应器流场以及气含率的影响。数值模拟结果表明：气相密度的改变对环流反应器内部的流场以及气含率几乎没有影响,而液相黏度改变对环流反应器轴向速度和气含率能产生较大的影响,液相密度改变能够对气含率产生较大影响。     

气井多液滴携液模型实验研究

在Zhou的多液滴模型基础上,通过可视化实验装置,采用压缩空气和水作为介质模拟气井气流携液过程,验证分析了Zhou的多液滴模型。通过大量实验数据分析发现：气体达到携液临界流速、持液率大于0.008 5时,气井开始出现积液,比Zhou所提出的0.010 0有所偏小;在持液率大于0.008 5时,加大气流速度到某值时,液体可以全部被携带出井口,且随着持液率的提高,所需的临界流速也随之增加。该文根据实验数据修正了Zhou的多液滴模型,提出了与实验数据相吻合的新模型,可用于高含水气井排水采气研究与工程实际应用。     

水平管段塞流持液率的试验统计分析

对水平管段塞流持液率进行了试验研究。通过对试验结果的统计分析可以得出:①可以利用段塞流持液率的波动情况来确定液塞频率。②在段塞流动中,当气相折算速度和液相折算速度相差不大时,持液率概率密度函数呈双峰分布;当液相折算速度不变时,随着气相折算速度的增大,持液率概率密度函数第2峰值逐渐减小,直至消失而变为单峰分布;利用这一特征可初步确定段塞流动中气、液相流量相对大小。③折算速度的变化会引起液塞持液率的变化,液塞持液率随气相折算速度的增大而减小,随液相折算速度的增大而增大。