Attractor comparison analysis for characterizing vertical upward oil gas water three-phase flow

We investigate the dynamic characteristics of oil-gas-water three-phase flow in terms of chaotic attractor comparison. In particular, we extract a statistic to characterize the dynamical difference in attractor probability distribution. We first take time series from Logistic chaotic system with different parameters as examples to demonstrate the effectiveness of the method. Then we use this method to investigate the experimental signals from oil-gas-water three-phase flow. The results indicate that the extracted statistic is very sensitive to the change of flow parameters and can gain a quantitatively insight into the dynamic characteristics of different flow patterns.

Quantitative research of the liquid film characteristics in upward vertical gas, oil and water flows

The study of liquid film characteristics in multiphase flow is a very important research topic, however,the characteristics of the liquid film around Taylor bubble structure in gas, oil and water three-phase flow are not clear. In the present study, a novel liquid film sensor is applied to measure the distributed signals of the liquid film in three-phase flow. Based on the liquid film signals, the liquid film characteristics including the structural characteristics and the nonlinear dynamics characteristics in three-phase flows are investigated for the first time. The structural characteristics including the proportion, the appearance frequency and the thickness of the liquid film are obtained and the influences of the liquid and gas superficial velocities and the oil content on them are investigated. To investigate the nonlinear dynamics characteristics of the liquid film with the changing flow conditions, the entropy analysis is introduced to successfully uncover and quantify the dynamic complexity of the liquid film behavior.

Rate transient analysis methods for water-producing gas wells in tight reservoirs with mobile water

Tight gas reservoirs with mobile water exhibit multi-phase flow and high stress sensitivity.Accurately analyzing the reservoir and well parameters using conventional single-phase rate transient analysis methods proves challenging.This study introduces novel rate transient analysis methods incorporating evaluation processes based on the conventional flowing material balance method and the Blasingame type-curve method to examine fractured gas wells producing water.By positing a gas-water two-phase equivalent homogenous phase that considers characteristics of mobile water,gas,and high stress sensitivity,the conventional single-phase rate transient analysis methods can be applied by integrating the phase's characteristics and defining the phase's normalized parameters and material balance pseudotime.The rate transient analysis methods based on the equivalent homogenous phase can be used to quantitatively assess the parameters of wells and gas reservoirs,such as original gas-in-place,fracture half-length,reservoir permeability,and well drainage radius.This facilitates the analysis of production dynamics of fractured wells and well-controlled areas,subsequently aiding in locating residual gas and guiding the configuration of well patterns.The specific evaluation processes are detailed.Additionally,a numerical simulation mechanism model was constructed to verify the reliability of the developed methods.The methods introduced have been successfully implemented in field water-producing gas wells within tight gas reservoirs containing mobile water.

An Experimental Study on the Flow Characteristics of OilWater Two-Phase Flow in Horizontal Straight Pipes

The flow patterns and their transitions of oil-water two-phase flow in horizontal pipes were studied. The experiments were conducted in two kinds of horizontal tubes, made of plexiglas pipe and stainless steel pipe with 40mm ID respectively. No. 46 mechanical oil and tap water were used as working fluids. The superficial velocity ranges of oil and water were: 0.04-1.2m·s^-1 and 0.04-2.2 m·s^-1, respectively. The flow patterns were identified by visualization and by transient fluctuation signals of differential pressure drop. The flow patterns were defined according to the relative distribution ofoil and water phases in the pipes. Flow pattern maps were obtained for both pipelines. In addition, semi-theoretical transition criteria for the flow patterns were proposed, and the proposed transitional criteria are in reasonable agreement with available data in liquid-liquid systems.

Oil–water two-phase flow pattern analysis with ERT based measurement and multivariate maximum Lyapunov exponent

Oil–water two-phase flow patterns in a horizontal pipe are analyzed with a 16-electrode electrical resistance tomography(ERT) system. The measurement data of the ERT are treated as a multivariate time-series, thus the information extracted from each electrode represents the local phase distribution and fraction change at that location. The multivariate maximum Lyapunov exponent(MMLE) is extracted from the 16-dimension time-series to demonstrate the change of flow pattern versus the superficial velocity ratio of oil to water. The correlation dimension of the multivariate time-series is further introduced to jointly characterize and finally separate the flow patterns with MMLE. The change of flow patterns with superficial oil velocity at different water superficial velocities is studied with MMLE and correlation dimension, respectively, and the flow pattern transition can also be characterized with these two features. The proposed MMLE and correlation dimension map could effectively separate the flow patterns, thus is an effective tool for flow pattern identification and transition analysis.

Multifractal analysis of inclined oil-water countercurrent flow

Characterizing countercurrent flow structures in an inclined oil-water two-phase flow from one-dimensional measurement is of great importance for model building and sensor design.Firstly,we conducted oil-water two-phase flow experiments in an inclined pipe to measure the conductance signals of three typical water-dominated oil-water flow patterns in inclined flow,i.e.,dispersion oil-in-water pseudo-slug flow （PS）,dispersion oil-in-water countercurrent flow （CT）,and transitional flow （TF）.In pseudo-slug flow,countercurrent flow and transitional flow,oil is completely dispersed in water.Then we used magnitude and sign decomposition analysis and multifractal analysis to reveal levels of complexity in different flow patterns.We found that the PS and CT flow patterns both exhibited high complexity and obvious multifractal dynamic behavior,but the magnitude scaling exponent and singularity of the CT flow pattern were less than those of the PS flow pattern; and the TF flow pattern exhibited low complexity and almost monofractal behavior,and its magnitude scaling was close to random behavior.Meanwhile,at short time scales,all sign series of two-phase flow patterns exhibited very similar strong positive correlation; at high time scales,the scaling analysis of sign series showed different anti-correlated behavior.Furthermore,with an increase in oil flow rate,the flow structure became regular,which could be reflected by the decrease in the width of spectrum and the difference in dimensions.The results suggested that different oil-water flow patterns exhibited different nonlinear features,and the varying levels of complexity could well characterize the fluid dynamics underlying different oil-water flow patterns.

Multi-scale complexity entropy causality plane: An intrinsic measure for indicating two-phase flow structures

We extend the complexity entropy causality plane（CECP） to propose a multi-scale complexity entropy causality plane（MS-CECP） and further use the proposed method to discriminate the deterministic characteristics of different oil-in-water flows. We first take several typical time series for example to investigate the characteristic of the MS-CECP and find that the MS-CECP not only describes the continuous loss of dynamical structure with the increase of scale, but also reflects the determinacy of the system. Then we calculate the MS-CECP for the conductance fluctuating signals measured from oil–water two-phase flow loop test facility. The results indicate that the MS-CECP could be an intrinsic measure for indicating oil-in-water two-phase flow structures.

碳酸盐岩缝洞型油藏流固耦合下的油水两相流动特征

为提高缝洞型碳酸盐岩油藏采收率,探究其流固耦合下的油水两相流动特性,根据不同介质中的流体流动规律,建立了Stokes-Darcy两相流体流动模型;基于有效应力原理和广义胡克定律,建立了适用于缝洞型碳酸盐岩油藏的油水两相Stokes-Darcy流固耦合数学模型;分别针对有无流固耦合的缝洞型碳酸盐岩油藏,进行了宏观和细观的油水两相流体流动模拟。研究结果表明:油藏有无流固耦合作用,其油水两相流体流动特性在基质区差异较大,在溶洞内差异较小,注水速度对缝洞型碳酸盐岩油藏的油水流动影响较大。

T型管油水分离效率的正交数值试验研究

T型管广泛应用于油田的油水分离,影响其分离效率的因素较多。运用正交试验方法对T型管的管径、垂直管间距、垂直管数等三个几何参数和含油率、进口速度和分流比等三个操作参数共计6因素3水平设计了18组试验方案,并运用计算流体力学数值模拟方法对其进行了数值试验研究,结果表明:各因素对T型管分离效率的影响大小为垂直管数>垂直管间距>分流比>含油率>入口流速>管径。管径60 mm、垂直管数3、垂直管间距1000 mm、含油率40%、入口流速0.35 m/s、分流比0.4为T型管的最优结构组合,此时T型管的分离效率达到99.99%。分离效率随垂直管数、垂直管间距的增加先降低再升高,随分流比、含油率的增加先升高再降低。管径和入口速度对分离效率的影响较小,其大小可视需要而定。

基于两相流的水封油库油气泄漏运移规律及控制措施

地下水封油库运行的关键是保持一定的水封厚度,为确定合适的水封厚度,基于气液两相流理论,采用有限元数值模拟方法,以我国某石油储备地下水封洞库为依托,模拟了地下水封石油洞库储油运行期油气的泄漏运移演变过程。结果表明:施工期不设置水幕系统情况下,洞室顶部出现了大面积的疏干区,造成后期无法储油;设置水幕系统情况下,洞库上方能够维持一定水封厚度,洞库周围岩层油气泄漏范围和泄漏量均与储油运行时间呈正幂函数关系;水封厚度越大油气泄漏范围和泄漏量越小,但过大的水封厚度会大大增加工程成本,所对应的案例在水封厚度为30 m时对油气泄漏控制最为经济合理,《地下水封石洞油库设计标准》推荐的水封厚度合理且有一定安全裕度。研究成果可为水封油库工程的设计及油气泄漏控制提供一定理论参考。

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。

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。

输油管道水相内部沉积特性研究

输油管线油水两相流输送水相沉积区是腐蚀重灾区,掌握水相沉积规律对管线的腐蚀防护具有重要的指导作用。为研究不同状况下输油管线水相积液对管道腐蚀的影响规律,模拟了不同含水率、倾角、流速等因素下的流型分布状况,探讨了不同流速、倾角、含水量下两相流流型分布规律,明确了流速在0.3~1.3m/s、1%~10%时水相沉积状态,发现倾角在30°时,水相沉积比较严重;汇总了管道内部出现的油水两相均匀流区、油水分层区和逆流沉积区三种状态,建立了不同含水率下流速-倾角-沉积状况表。通过现场管道泄漏点分布验证,危险管段分布特征与模拟结果基本吻合。

基于四电极电磁流量计的水平井油水两相流实验研究

在水平井油水两相流测量中,传统的两电极电磁流量计在流量1~40 m^(3)/d时测不到准确的流量数据。为扩大其适用范围,研发了四电极电磁流量计。该流量计由2个呈90°交叉排列的两电极电磁流量计构成,在油水两相流模拟水平井中,采用全集流方式进行流量测量实验。结果表明:四电极电磁流量计解决了在流量1~5 m^(3)/d、含水率90%以上时两电极流量计因传感器在油相中而得不到准确流量数据的问题;在流量5~40 m^(3)/d、含水率80%~90%时解决了流量测量值波动较大的问题。与两电极电磁流量计相比,四电极电磁流量计扩大了测量范围,提高了测井成功率和测量精度。

基于SPH方法的围油栏仿真研究

为解决计算流体动力学(computational fluid dynamics,CFD)方法在模拟围油栏围控溢油时流-固耦合、水-油液体两相流中的不稳定性、计算效率差、将自由表面视为滑移壁且不考虑围油栏移动等问题,基于光滑粒子流体动力学(smoothed particle hydrodynamics,SPH)方法建立适用于围油栏围控溢油的固-液耦合、液体两相流数值模型,将5种不同裙摆结构的围油栏导入两相液体相互作用的数值仿真模型中,通过SPH代码设定数值模拟相关参数,提高计算效率,得到较精确的围油栏滞油长度与溢油失效步长。结果表明:围油栏围控溢油能力与上、下裙摆高度比及裙摆角类型有关,上裙摆高度占比越大,围油栏的滞油表现越好;前折角型围油栏的滞油表现优于前转角型围油栏;滞油长度与油品性质有关,油品的密度和黏度越小,围油栏的滞油长度越大。

喷气燃料上倾管道油水两相流动规律仿真研究

随着民航行业的快速发展,广泛使用管道运输喷气燃料。但是管道中的水分容易在低洼处聚积,并带来腐蚀和流动不畅等一系列问题。基于计算流体力学(CFD)方法对不同倾角上倾管道中喷气燃料携带底部积水情况进行了计算机仿真。计算结果表明,随着时间的增加,在喷气燃料的剪切作用下,管底积水将被分成大水团和小水滴两部分;随着倾角的增大,大水团的轴向长度变短,相界面波动剧烈,导致管底水相出现回流现象进而流动速度变缓。

Hydrate Prevention Strategies and the Associated Cost in the Gulf of Mexico

With the petroleum industry endeavoring to develop promising oil and gas in deeper water, gas hydrates prevention is a serious concern for oil and gas producing companies producing at conditions in the hydrate region. This paper details lessons learned from the successful field deployment of AA LDHI and proper implementation strategies used for 3 different practical fields as case studies in the Gulf of Mexico. From the 3 field experiences, the AA LDHI has been used to replace the conventional thermodynamic hydrate inhibitor due to its numerous benefits during steady state operations and transition operations where AA LDHI is injected prior to extended shut in and restart for fields producing at low water cut. However, the strategy to develop a cost effective chemical management of hydrates for fields producing at high water cut is by pumping methanol or diesel to push down the wellbore fluid below the mud line during planned and unplanned shut-ins to delay water production, it also secures the riser with non hydrate fluids. This illustrates how the AA LDHIs are used in conjunction with more conventional hydrate management approaches to reach an optimal cost effective field hydrate management solution. However, this shows that the key to overall success of hydrate prevention is a full integration of a good front end design, a comprehensive deployment and an effective down hole monitoring system.

油气混输工艺在低输量管道安全运行中的优势分析

为了保证华北油田某区块J-S输油管道能够在低输量下安全运行,对比分析油气混输和低含水油输送两种技术方案,优选通过油气混输的运行方式降低J-S输油管道最低启输量和启输温度。通过在J站新建伴生气压缩、注入、放空系统,在S站新建分离、过滤、放空系统,利用两相流在管道中的流动特性,提高管道内介质流速,并将J站富余的伴生气资源通过管输的方式输送至S站。设计采用PIPESIM软件及HYSYS软件进行模拟,计算结果相互验证。该方案不但解决了J-S输油管道低输量下安全运行的问题,同时缓解了J油田与S油田伴生资源分布不均匀的矛盾,降低了油田原油生产成本。

A MODEL FOR PREDICTING PHASE INVERSION IN OIL-WATER TWO-PHASE PIPE FLOW

Experiments of phase inversion characteristics for horizontal oil-water two-phase flow in a stainless steel pipe loop （25.7 mm inner diameter,52 m long） are conducted. A new viewpoint is brought forward about the process of phase inversion in oil-water two-phase pipe flow. Using the relations between the total free energies of the pre-inversion and post-inversion dispersions, a model for predicting phase inversion in oil-water two-phase pipe flow has been developed that considers the characteristics of pipe flow. This model is compared against other models with relevant data of phase inversion in oil-water two-phase pipe flow. Results indicate that this model is better than other models in terms of calculation precision and applicability. The model is useful for guiding the design for optimal performance and safety in the operation of oil-water two-phase pipe flow in oil fields.

水平井油水两相流阵列电磁波持水率计算方法及应用

准确求取水平井多相流持水率和反演井筒流体分布是揭示水平井开发动态的关键基础,以国产阵列电磁波持水率计为切入点开展研究,在对比分析现有阵列持水率定量计算方法基础上,提出了一种基于阵列探头径向投影中点切分面积计算持水率方法,同时对比建立了水平井筒油水两相流高、中、低含水率条件流体介质分布反演方法。研究表明,新方法计算水平井持水率平均绝对误差为4.43%,相对误差为16.34%,明显优于目前采用的权系数法和径向等高面积法;同时,高、中、低含水条件水平井筒流体分布反演以高斯径向基函数法和多元线性法最为匹配,研究成果为矿场水平井多相流生产动态评价奠定基础。