Doppler spectrum analysis and flow pattern identification of oil-water two-phase flow using dual-modality sensor

Horizontal oil-water two-phase flow widely exists in petroleum and chemical engineering industry, where the oil and water are usually transported together. As one of most importance process parameters to describe the two-phase flow, the flow pattern can reflect the flow characteristics of inner flow structure and phase distribution. The identification of flow pattern will contribute to develop more accurate measurement model for flow rate or phase fraction and ensure the safety and efficiency of operation in industry. A dual-modality sensor combining with continuous wave ultrasonic Doppler sensor (CWUD) and auxiliary conductance sensor, was proposed to identify flow patterns in horizontal oil-water two-phase flow. In particular, the oil-water flow characteristic was analyzed from Doppler spectrum based on the CWUD sensor. Besides, the dimensionless voltage parameter based on conductance sensor was applied to provide the information of continuous phase in the fluid. Several statistical features were directly extracted without any complicated processing algorithm from Doppler and conductance signals. The extracted features are put into a multi-classification Support Vector Machine (SVM) model to classify five oil-water flow patterns. The results show that the overall identification accuraccy of 94.74% is satisfactory for horizontal oil-water two-phase flow. It also demonstrates that the noninvasive ultrasonic Doppler technique not only can be used for flow velocity measurement but also for flow pattern identification.     

Coriolis mass flow metering for three-phase flow: A case study

Previous work has described the use of Coriolis mass flow metering for two-phase (gas/liquid) flow. As the Coriolis meter provides both mass flow and density measurements, it is possible to resolve the mass flows of the gas and liquid in a two-phase mixture if their respective densities are known. To apply Coriolis metering to a three-phase (oil/water/gas) mixture, an additional measurement is required. In the work described in this paper, a water cut meter is used to indicate what proportion of the liquid flow is water. This provides sufficient information to calculate the mass flows of the water, oil and gas components. This paper is believed to be the first to detail an implementation of three-phase flow metering using Coriolis technology where phase separation is not applied.Trials have taken place at the UK National Flow Standards Laboratory three-phase facility, on a commercial three-phase meter based on the Coriolis meter/ water cut measurement principle. For the 50 mm metering system, the total liquid flow rate ranged from 2.4 kg/s up to 11 kg/s, the water cut ranged from 0% to 100%, and the gas volume fraction (GVF) from 0 to 50%. In a formally observed trial, 75 test points were taken at a temperature of approximately 40 °C and with a skid inlet pressure of approximately 350 kPa. Over 95% of the test results fell within the desired specification, defined as follows: the total (oil+water) liquid mass flow error should fall within ±2.5%, and the gas mass flow error within ±5.0%. The oil mass flow error limit is ±6.0% for water cuts less than 70%, while for water cuts between 70% and 95% the oil mass flow error limit is ±15.0%.These results demonstrate the potential for using Coriolis mass flow metering combined with water cut metering for three-phase (oil/water/gas) measurement.     

一种永置式石油生产地面多井组单井轮巡 三相流监测装置及应用研究

为了解决传统石油开发集中计量方式难以获取单口油井油气水三相流相关参数的难题,采用流体体积和有限元分析等方法在建立该测量装置的数值仿真模型基础上对其结构参数、气液分离效果等进行了深入研究与优化,从而确定了该监测装置的最优结构参数,并研制了可以在现有集中计量环境中长期、稳定与可靠使用的一种永置式石油生产多井组单井轮巡三相流监测装置。另外,还在搭建的永置式石油生产地面多井组单井轮巡三相流多参数监测平台上开展了实验研究,实验结果表明,所研制的装置在气、液相流量5～70 m³/d,液相持水率50%～90%等混合流体下持水率、气量测量误差均小于10%,流量测量误差小于4%。仿真和实验均证明了永置式监测装置具有良好的多分相测量性能。     

A flow rate measurement method for horizontal oil-gas-water three-phase flows based on Venturi meter,blind tee,and gamma-ray attenuation

Online horizontal oil-gas-water three-phase flow rate monitoring is essential for reliable operations during industrial production. A flow rate measurement method is developed in horizontal oil-gas-water three-phase flows by combining a blind tee, a Venturi meter, and a gamma-ray densitometer. The blind tee is installed at the test section entrance to homogenize the mixture by transforming the horizontal flow to a vertical upward flow. The Venturi meter is used for the total flow rate measurement. The dual-energy gamma-ray densitometer is used for phase holdup measurement. In the present method, blind-tee mixing effects and oil-water mixture slip behavior is essential, which were experimentally analyzed in this work. The phase inversion was found in the oil-water mixture with the increasing of the oil volume fraction. Besides, the addition of the gas reduces the oil-water slip ratio. For the range of 0–35% and 65–100% oil fraction in the oil-water liquid, the oil-water mixture can be well treated as a pseudo homogenous liquid with a slip ratio of 0.9–1.1. A three-phase flow rate model is then established for these conditions. The method was validated by horizontal oil-gas-water three-phase flows with average relative errors of 3.2% for the total flow rates, 4.3% for the gas flow rates, 11.5% for the oil flow rates, and 7.8% for the water flow rates.     

原油含水率红外光谱测量的超稀疏表示方法

油水混合物的光谱分析方法已经成为当前油水两相流测量的研究热点。然而,传统的油水混合物光谱分析中,一般是通过主成分分析、连续投影算法等降维技术实现其光谱特征提取,所提取光谱数大多在10条以上,这使得油水两相测量光纤式传感器的制造成本很高且工程实现难度很大。为提高基于光谱分析的油水两相测量光纤式传感器的实用性,需要实现油水两相红外光谱的超稀疏表示。为此提出了油水混合物光谱自-互相关联合(self-cross correlation,SCC)的光谱超稀疏表示方法。为了验证方法的有效性,搭建了油水混合物红外光谱含水率测量实验装置,从SCC算法筛选出的6个波段中,根据实际生产工艺选择了1 050 nm和1 650 nm波段进行动态实验,实验结果表明,1 050 nm和1 650 nm波段对油和水的混合流型响应良好,且两者呈现出了显著的互相关性。显然,本文研究有助于提升工业光纤式传感器的使用性能。     

自力式油气水三相流气液分离装置的设计与实验

针对油井油气水三相流量测量难、测准更难这一实际问题,对溢气型集流伞的结构作了优化和改进,设计出一种自力式油气水三相流气液分离装置,装置上安装了涡轮流量计和电导持水率计,完成油气水产出剖面测井仪的研制。利用多相流测试系统对产出剖面测井仪进行了流量测量实验,实验结果表明,产出剖面测井仪能有效降低油井气相对油井液相流量和持水率测量的影响,可提高油田测量精度及采收率。     

Theoretical study of vertical slug flow measurement by data fusion from electromagnetic flowmeter and electrical resistance tomography

Electrical resistance tomography (ERT) can be used to obtain the conductivity distribution or the phase distribution of gas/liquid flows (e.g. slug flow). Using proper parameter models and flow regime identification models, the measurement of phase size, void fraction, and pattern recognition can be realized. Electromagnetic flowmeters have been used to measure conductive single-phase liquid flows. However, neither ERT nor electromagnetic flowmeters (EMF) can provide accurate measurement of gas/liquid two-phase flows. This paper presents an approach to fuse the information from ERT and an electromagnetic flowmeter. A model for the measurement signal from the electromagnetic flowmeter has been developed based on the flow pattern and the phase distributions, which are obtained from the reconstructed images of ERT, aiming to reduce the measurement error of the electromagnetic flowmeter and enhance the measurement accuracy. Through the simulation research of virtual current density distribution, the feasibility of fusion of electromagnetic flowmeter and ERT to measure gas/liquid two-phase vertical slug flow is verified. By theoretical analysis, the relationship between the output of electromagnetic flowmeter and flow parameters is established. The electrical potential difference of the electromagnetic flowmeter, average velocity, volume flow rate and gas void fraction between the bubble size and location are also investigated. The fusion approach can be used to measure vertical slug flows.     

Review of oil–water through pipes

In oilfield operations, co-current flow of oil–water mixture is very common and can cause significant flow assurance problems during production. Accurate knowledge of behaviour of oil–water in a pipeline flow is crucial to design/optimize production, transportation, and processing facilities. Many researchers have attempted to generalize the liquid–liquid or the two phase flow systems through mechanical models and develop means for predicting the flow patterns, pressure drop, and water holdups. However, the crude oil properties differ and the oil–water system can be operated over various range of operating conditions and subsequently encounter an altered hydrodynamics behaviour in two phase flow system. To worsen the situation, almost all the empirical correlations and mechanical models developed were for low viscosity oil and with majority focused on gas–liquid flow. Thus, comprehensive models still remain unsolved for some of the flow issues especially when involving high viscosity or waxy crude oils. Hence an attempt to generalize liquid–liquid flow in multiphase systems seems impractical. Since conventional light crude oil or easy oil reserves are gradually depleted, thus many research works on high viscosity oil–water flow in pipes have been initiated. Presently, there is limited number of papers on high viscous oil–water flow in open literature which has confined the understanding of the flow behaviour of two-phase flow. In this communication, we report a review on the current state of research on two phase flow oil–water phenomena, highlighting what is so far has been realized and how this knowledge can be applied as a basis to understand better of the more complex cases of gas-crude oil–water three phase flow.     

Voidage measurement of gas–liquid two-phase flow based on Capacitively Coupled Contactless Conductivity Detection

Based on Capacitively Coupled Contactless Conductivity Detection (C⁴D) technique, a new method for the voidage measurement of conductive gas–liquid two-phase flow is proposed. 15 Conductance signals, which reflect voidage distribution of gas–liquid two-phase flow, are obtained by a six-electrode C⁴D sensor. With the conductance signals, the flow pattern of gas–liquid two-phase flow is identified by flow pattern classifiers and then the voidage measurement is implemented by a corresponding voidage measurement model (for each typical flow pattern, a corresponding voidage measurement model is developed). The conductance measurement of the six-electrode C⁴D sensor is implemented by phase sensitivity demodulation (PSD) method. The flow pattern classifiers and the voidage measurement models are developed by partial least squares (PLS) technique and least squares support vector machine (LS-SVM) technique. Static voidage measurement experiments and dynamic voidage measurement experiments show that the proposed voidage measurement method is effective, the developed six-electrode C⁴D sensor is successful and the measurement accuracy is satisfactory.     

Electrical capacitance tomography for gas–solids flow measurement for circulating fluidized beds

Gas–solids flows in the risers of circulating fluidised beds (CFBs) and cyclones exhibit complex physical behaviour, such as local backflow and recirculation. The difficulties in accurate measurement of gas–solids flows stem from various flow regimes, which exist in multi-phase flows in pipelines and vessels. It is necessary to investigate the solids’ fraction profile, flow regime identification, image reconstruction, flow acceleration and flow velocity. Electrical capacitance tomography (ECT) is regarded to be a successful technology for imaging industrial processes containing dielectric materials. ECT would help understanding of gas–particle interaction, particle–boundary interaction and the influence of gas on the solids’ flow turbulence.The first part of this paper covers some new developments in ECT, i.e., algorithms for 3D image presentation and on-line iterative image reconstruction. The second part presents a novel non-intrusive technique for measuring axial and angular velocities. Theoretical and experimental studies, carried out using cross-correlation techniques in a cyclone separator dipleg, confirm the feasibility of on-line velocity measurement. Experimental results from various gas–solids flow facilities, CFB and cyclone, are presented.     

Sectional void fraction measurement of gas-water two-phase flow by using a capacitive array sensor

The sectional void fraction measurement for multiphase flow is usually influenced by flow patterns. Inspired by electrical capacitance tomography (ECT) devices applied to flow imaging (whose measured capacitance data contain both the flow pattern and sectional void fraction information), a capacitive array sensor is developed to realize two functions, flow pattern recognition and void fraction measurement, simultaneously; so that the void fraction measurement can be conducted for a certain flow pattern and the measurement accuracy can be expected to be improved. The main idea of the proposed method can be described as: firstly, the proper feature vectors are extracted from the electrical signal to identify the flow pattern (the BPNN model with GDX learning algorithm is used for flow pattern identification); and then the average of electrical signal is applied to estimates the void fraction by the corresponding calibration curve. An experimental platform of air/water two-phase flow is built (on which 3 flow patterns can be generated stably) to test the performance of the proposed method. The results support the correctness and effectiveness of the proposed method.     

Measuring phase distribution in high pressure three-phase flow using gamma densitometry

A large campaign of multiphase experiments using formation water, a North Sea crude oil and a blend of gas produced from different North Sea gas fields was performed in the Porsgrunn Multiphase Flow Loop. The tests were performed under realistic field conditions (p=100 bar and ). Different multiphase flow patterns such as waves and slugs were observed in the experiments. At high pressure conditions it is often difficult to distinguish between these types of flows due to considerable dispersions between the fluid phases.A traversable dual-energy gamma instrument was used to measure phase fractions at different positions at 7 Hz. Careful data analysis was needed to obtain the relevant data from the noisy measurements. Data analysis techniques for three-phase flow were developed and tested against calibration data from single-phase and two-phase flow.In addition it was shown that the averaged density data from the traversable gamma instrument compared favourably to density measurements by a calibrated stationary single-energy gamma instrument.However the traversable densitometer gave much more additional information compared with the single-energy instrument since the transient phase fraction for all three phases could be measured at different positions over the cross section of the pipeline. This information allowed the definite determination of the flow pattern.     

多相流分相含率检测

介绍了基于双能射线对油气水多相流分相含率的测量机理及系统构成 ,通过对射线穿过原油的透射计数 ,并对各种误差进行补偿、修正 ,从而实现对多相流分相含率的在线测量     

Salinity and flow regime independent multiphase flow measurements

For oil production fields, there is a need for downhole measurements of the gas/water/oil multiphase flow. In extreme conditions a relatively simple, robust, and non-intrusive system will be appropriate. A measurement setup that combines multiple gamma beam (MGB) and dual modality densitometry (DMD) measurements, would be able to determine the gas volume fraction (GVF) independently of the flow pattern, and monitor changes in water salinity. MGB measurements of gamma-ray transmission along multiple sections across the oil pipe will provide information on the flow pattern. Whereas the DMD principle will give information on changes in salinity from a combination of transmission and scattering gamma-radiation measurements. In this work we present the results from MGB and DMD measurements of a multiphase flow with high-speed gamma-ray tomograph measurements as reference for the flow pattern. The MGB measurements should enable us to distinguish between stratified or wavy/slug and annular or slug flow. Flow patterns with several minor components distributed evenly over the measurement cross section, like bubble flow, will be interpreted as homogeneous flow. The DMD measurements can be used to monitor salinity changes of the water component for intervals where the GVF is low and the water cut of the liquid is high. Combined with other gauges for water cut measurements, the MGB and DMD measurement setup should improve the multiphase flow measurements, and enable increased oil/gas recovery and production water monitoring.     

On-line measurement of oil/gas/water mixtures,using a capacitance sensor

This paper describes the use of a non-intrusive capacitance transducer for the simultaneous on-line measurement of water and undissolved gas in crude oil. The water concentration of the flow is determined from the mean capacitance of the flowing mixture. The same transducer can be used simultaneously to determine the void fraction of the flow by measuring the instantaneous variation in the permittivity of the mixture created by fluctuations of the gas component. There is an interaction between these two measurements but this can be decoupled. This measurement principle was investigated experimentally, using process oil/water/air mixtures. Results are reported for mixtures with water contents up to 40% v/v and void fractions up to 15% v/v.A three-component volumetric flowrate measurement system, based on the capacitance transducer discussed in this paper was proposed. The work reported and the conclusions drawn relate to tests using mixtures of lubricating oil/fresh clean water/air. No work has so far been carried out in mixtures of crude oil/saline waters/hydrocarbon gases typical of the intended applications, nor have estimates been made of the effects that the variable nature of these actual components might have on the performance of the technique. Also, the tests were made on a Perspex section of pipe at nominal pressure whereas the real-life application would require measurements on a high-pressure/high-integrity stell pipeline; the practical problems of adapting the technique to the latter situation have not been examined though they are considered to be resolvable.     

A study on the relationship between upstream and downstream conditions in swirling two-phase flow

Inline fluid separation is a concept, which is used in the oil and gas industry. Inline fluid separators typically have a static design and hence changing inlet conditions lead to less efficient phase separation. For introducing flow control into such a device, additional information is needed about the relationship of upstream and downstream conditions. This paper introduces a study on this relationship for gas/liquid two-phase flow. The downstream gas core development was analyzed for horizontal device installation in dependence of the inlet gas and liquid flow rates. A wire-mesh sensor was used for determining two-phase flow parameters upstream and a high-speed video camera to obtain core parameters downstream the swirling device. For higher accuracy of the calculated void fraction, a novel method for wire-mesh sensor data analysis has been implemented. Experimental results have shown that void fraction data of the wire-mesh sensor can be used to predict the downstream behavior for a majority of the investigated cases. Additionally, the upstream flow pattern has an impact on the stability of the gas core downstream which was determined by means of experimental data analysis.     

Effects of flow patterns and salinity on water holdup measurement of oil-water two-phase flow using a conductance method

This research investigates the effects of flow pattern and salinity of oil-water two-phase flow on water holdup measurement using a conductance method. Firstly, vertical upward oil-water two-phase flow experiment is conducted in a 20 mm inner diameter (ID) pipe, in which the salinities of aqueous solutions are set as 151 ppm, 1003 ppm, 2494 ppm and 4991 ppm respectively. Experimental water-cut and mixture velocity are set as 80–100% and 0.0184–0.2576 m/s. In the experiment, three different flow patterns, i.e., dispersed oil-in-water slug flow (D OS/W), dispersed oil-in-water flow (D O/W) and very fine dispersed oil-in-water flow (VFD O/W) are observed and recorded by a high speed camera. Meanwhile, we collect the response of Vertical Multiple Electrode Array (VMEA) conductance sensor excited by a sine voltage signal. The result shows that, for VFD O/W, the water holdup from VMEA sensor shows a satisfied agreement with that of quick closing valve (QCV) method under certain salinities, i.e., 1003 ppm as well as 2494 ppm. For D OS/W flow and D O/W flow characterized by dispersed oil droplets with various sizes, considerable deviations of water holdup between VMEA sensor and QCV method under four kinds of salinity aforementioned are presented. Afterward, according to experimental analysis along with theoretical deviation, it is concluded that the deviation of the measurement system reaches its minimum when reference resistance in the measurement circuit and salinity of the aqueous solution satisfy constraint conditions, and the accuracy of water holdup using the conductance method can be improved through adjusting reference resistance to match the salinity of water phase. Finally, the recurrence plot algorithm is utilized to identify typical flow patterns mentioned above and it shows satisfied results on comprehending the discrepancies among different flow patterns, demonstrating that the recurrence plot algorithm can be effectively applied in flow pattern identification regarding oil-water flows.     

油气水三相流产出剖面光纤持气率计响应规律的实验研究

为进一步研究油气水三相流产出剖面测井中光纤持气率计在高含水情况下的响应规律,在大庆油田多相流实验装置上进行了动态实验研究。实验结果表明,当油的流量一定,高含水的情况下,气量在5~10m3/d变化时测量持气率值与实际持气率值之间误差变化较大。气量大于10m3/d时误差变化较小,说明该仪器适合测量气量在10m3/d以上的混合流体。此结果对光纤持气率计的进一步优化设计提供了实验依据。     

Simulation and experimental study of phase segregation in helical pipes: A new method for flow conditioning

The aim of the present study is to contribute some knowledge of phase separation phenomena of gas–liquid turbulent flow in curved pipe and provide a basis for the development of an in-line gas–liquid separator and flow pattern conditioning device. A systematic study of gas–liquid three-phase flow in 3D helical pipes was numerically performed. Gas phase distribution in the flow through the helical pipe was analyzed for various flow parameters conditions and different pipe geometries. Experimental qualitative results show that a helical pipe can, successfully, be used to condition a bubble flow into a stratified (stratified wavy flow). The main idea is to put it just upstream of sensors that are flow regime dependent; ensuring that the sensor, once calibrated to work in this flow pattern, suffers no reduction in its performance and, consequently, avoid additional sources of error.     

Flow pattern identification for gas-oil two-phase flow based on a virtual capacitance tomography sensor and numerical simulation

Gas-oil two-phase flow is widely encountered in oil exploitation and transportation pipelines. It's complex and transient changes of flow regimes present a great challenge for accurate and real-time measurement. As a non-invasion and real-time measuring method, electrical capacitance tomography (ECT) is suitable for the transient measurement of non-conductive gas-oil flow. However, the highly random and nonlinear nature of multiphase flow make it difficult and limited to investigate the flow parameters based on either static or dynamic measurement. In this research, the whole process of dynamic measurement of ECT applying in gas-oil two-phase flow is thoroughly studied, including simulation calculation, experimental validation and comprehensive data analysis. A simulation approach by coupling the flow and electrostatic field is proposed based on a virtual ECT sensor, in order to monitor the gas-oil two-phase flow characteristics. Based on FLUENT and COMSOL platform, the numerical simulation under six typical flow patterns in a horizontal pipe is carried out. Combining the visualized image generated by ECT measurement and the theory of flow pattern transition, the formation mechanism and structural characteristics of different gas-oil flow patterns are analyzed in detail. Furthermore, this research attempts to analyze the signal fluctuation characteristics caused by flow pattern change, in order to access more in-depth flow information implied in the original capacitance data, via time-series analysis as well as frequency domain analysis based on Flourier Transform. At last, a series of dynamic experiment is conducted to verify the feasibility of the simulation and data analysis approach. The experiment focuses on the flow pattern transition, gas-liquid dynamic characteristics and noise influence in the actual process. It can be concluded from the results of simulation and experiment tests, combining the visualized images and the dynamic characteristics of capacitance signals can make it more effective and intuitive for flow pattern identification, which might be used for the online measurement in real-industry process.