Multiphase flow measurements using coupled slotted orifice plate and swirl flow meter

Multiphase flow metering is a major focus for oil and gas industries. The performance of a modified version of a close coupled slotted orifice plate and swirl flow meter for multiphase flow was evaluated to provide further development of a new type of multiphase flow meter. The slotted orifice provides well homogenized flow for several pipe diameters downstream of the plate. This characteristic provides a homogeneous mixture at the inlet of the swirl meter for a wide range of gas volume fractions (GVF) and flow rates. In order to evaluate the performance of the designed flow-meter, its response was investigated for varying pressures and water flow rates. The proper correlations were established to provide high accurate two-phase flow measurements. The new proposed approach provides the GVF measurement with less than ±0.63% uncertainty for GVF range from 60% to 95%.     

Estimation of flow rates of individual phases in an oil-gas-water multiphase flow system using neural network approach and pressure signal analysis

Up until now, different methods, including; flow pressure signal, ultrasonic, gamma-ray and combination of them with the neural network approach have been proposed for multiphase flow measurement. More sophisticated techniques such as ultrasonic waves and electricity, as well as high-cost procedures such as gamma waves gradually, can be replaced by simple methods. In this research, only flow parameters such as temperature, viscosity, pressure signals, standard deviation and coefficients of kurtosis and skewness are used as inputs of an artificial neural network to determine the three phase flow rates. The model is validated by the field data which were obtained from separators of two oil fields and 6 wells over ten-month with 8 h interval (totally 5400 sets of data). A linear relation can be observed between the actual data and the predictions which were obtained from separators and neural network approach, respectively. Furthermore, it is shown that using feed forward neural network with Levenberg–Marquardt algorithm which has two hidden layers is sufficient to determine the flow rates. Also, it is tried to see the effect of flow regimes on the results of neural network approach by determining kurtosis and skewness coefficients for different flow regimes in a horizontal pipeline.     

Wet gas metering with a horizontally mounted Venturi meter

Wet gas metering is becoming an increasingly important problem to the Oil and Gas Industry. The Venturi meter is a favoured device for the metering of the unprocessed wet natural gas production flows. Wet gas is defined here as a two-phase flow with up to 50% of the mass flowing being in the liquid phase. Metering the gas flowrate in a wet gas flow with use of a Venturi meter requires a correction of the meter reading to account for the liquids effect. Currently, most correlations in existence were created for Orifice Plate Meters and are for general two-phase flow. However, due to no Venturi meter correlation being published before 1997 industry was traditionally forced to use these Orifice Plate Meter correlations when faced with a Venturi metering wet gas flows. This paper lists seven correlations, two recent wet gas Venturi correlations and five older Orifice Plate general two-phase flow correlations and compares their performance with new independent data from the NEL Wet Gas Loop with an ISA Controls Ltd. Standard specification six inch Venturi meter of 0.55 beta ratio installed. Finally, a new correlation is offered.     

Calculation of the virtual current in an electromagnetic flow meter with one bubble using 3D model

Based on the theory of electromagnetic induction flow measurement, the Laplace equation in a complicated three-dimensional (3D) domain is solved by an alternating method. Virtual current potentials are obtained for an electromagnetic flow meter with one spherical bubble inside. The solutions are used to investigate the effects of bubble size and bubble position on the virtual current. Comparisons are done among the cases of 2D and 3D models, and of point electrode and large electrode. The results show that the 2D model overestimates the effect, while large electrodes are least sensitive to the bubble. This paper offers fundamentals for the study of the behavior of an electromagnetic flow meter in multiphase flow. For application, the results provide a possible way to estimate errors of the flow meter caused by multiphase flow.     

The development of a multiphase flow meter without separation based on sloped open channel dynamics

The online continuous measurement of multiphase flow is one of the most key technologies which influences the development of oil industry in future. A new type of multiphase meter system is developed based on the open channel flow. The test pipe of the meter is slightly slopped to make the flow pattern mainly stratified flow. Based on the study of oil and gas flow dynamics in the open channel test pipe, the liquid metering model and gas metering model are deduced to calculate the gas and the liquid flow rate, the water cut is measured online by the principle of differential pressure. This device can work online without the separation of the production fluid. By the lab test and field application test, the results of the metering system show that the liquid flow rate errors are within ±5%, the gas flow rate errors can be within ±5%, and the water cut absolute error is within ±2%, which can meet the demands of the field flow rate measurement.     

Time resolved measurement of pulsating flow using orifices

This article reviews the theoretical background of the measurement of pulsating flow using orifices as flow to pressure transducers, providing a synopsis of work done in this field. Special attention is paid to the temporal inertia and the applicability of expressions thereof given in the literature. Other factors influencing the measurement, such as changing flow profiles and the effect of connection tubes between the pressure sensor and the orifice are discussed. An experiment was performed to investigate the applicability of an equation taking reverse flow and temporal inertia into account for the measurement of pulsating flow with relative pulsation amplitudes around 1 and frequencies up to 50 Hz. It was found that the suggested equation may give tolerable results if the ratio of the pulsating part of the velocity to the angular frequency times orifice diameter is not too high. For high ratios, however, the results could not be explained by the suggested equation.     

Particle image velocimetry investigations on multiphase flow in fluidized beds: A review

Fluidized Beds (FBs) are widely employed in the petroleum and coal energy sector because they offer excellent contact, both in terms of high surface area and long times. The last two decades has seen measurement on multiphase flows shift from conventional pressure sensors to direct flow image acquisition and processing. Particle Image Velocimetry or PIV, and PIV coupled with Digital Image Analysis or DIA, are used to directly and instantaneously acquire flow field data to make hidden flow patterns and flow structures discoverable. Research abounds on Gas-Solid FB hydrodynamics using PIV, but Liquid-Solid and Gas-Liquid-Solid systems are only slowly catching up. Similarly, the use of Geldart B and D particles for such studies is very common, whereas A and C type particle hydrodynamics is as yet largely unexplored by using imaging. Turbulence, high temperature, particle clusters, particle agglomeration and dense particle flows pose particular challenges to using PIV in FB. The two-zone FB and micro-FB warrant further attention. Small sized A & C type particles of rod-like, plate-like and angular shape provide huge scope for PIV investigations on FBs in the future. This review provides a concise account of several PIV studies on all types of FBs with focus on the past two decades, and also details the limitations of PIV measurements with future scope of work.     

Three-way PLS regression and dual energy gamma densitometry for prediction of total volume fractions and enhanced flow regime identification in multiphase flow

Dual energy gamma densitometry and 3-way partial least squares regression were applied to quantify the total volume fractions and improve flow regime identification in multiphase flow. Multiphase flow experiments were carried out with formation water, crude oil and gas from different North Sea gas fields in Statoil׳s High Pressure Multiphase Flow Loop in Porsgrunn, Norway. Four different flow regimes were investigated (stratified wavy, slug, dispersed and annular). A traversable dual energy gamma densitometer was used to measure the fluid densities in the pipe. Partial least squares regression was previously applied to identify multiphase flow regimes and quantify volume fractions of gas, oil and water. That study showed promising results for flow regime identification but the predictions of the total volume fractions were not acceptable. In this study a new method combining gamma densitometry and 3-way partial least squares regression was applied in order to improve the quantitative estimation of the total volume fractions gained in the previous study. The proposed 3-way regression approach allows prediction of the total volume fractions directly using one model instead of multiple models which was reported earlier. The improved quantification of the volume fractions of gas, oil and water was used to improve the flow regime identification plots and increase the interpretability.The new 3-way prediction results for the volume fractions were significantly better than what was found earlier based on individual PLS models. The root mean square error of prediction for gas, oil and water from the 3-way PLS models were 4.1 %, 4.3 % and 4.6% respectively. All models reported were validated based on independent data (test set validation).     

Two-phase flow metering of heavy oil using a Coriolis mass flow meter: A case study

The use of Coriolis mass flow metering for two-phase (gas/liquid) flow is an emerging theme of both academic research and industrial application. The key issues are maintaining flow-tube operation, and modelling and correcting for the errors induced in the mass flow and density measurements. Experimentally-derived data is used to illustrate that these errors vary most notably with gas void fraction (GVF) and liquid flow rate, but other factors such as flow-tube geometry and orientation, and fluid properties such as viscosity are also influential. While undoubtedly a universal two-phase flow correction model is the ultimate research goal, there is currently no obvious candidate to explain the range of behaviours observed. This paper describes and demonstrates an empirical methodology that has proven effective in developing good correction models for a given choice of Coriolis flow-tube and flow mixture.

A growing proportion of the world’s oil reserves may be described as “heavy”, implying high density and high viscosity. Of the various metering challenges heavy oil poses, one of the most significant is its ready entrainment of gas, and the difficulties entailed in separating gas from the oil. Accurate two-phase measurement of heavy oil is therefore an especially desirable technical goal.

Trials were carried out at the National Engineering Laboratory (NEL), Scotland on a 75 mm flowmeter using a high viscosity oil. Flowrates from 1 kg/s to 10 kg/s were examined, with gas void fraction (GVF) up to 80%. The resulting models were tested online in a commercial Coriolis mass flow meter and demonstrated good performance for both steady and slugging two-phase flows, with the corrected measurements typically within 1%–5% of the nominal mass flow and density.

Field trials in Venezuela have confirmed the performance of this two-phase solution.

While research continues into the development of a generic two-phase correction, this case study demonstrates that the current state of the art can provide, for economically important fluids, tailored models with good two-phase flow performance.     

Direct numerical simulation of multiphase flow for arbitrary geometry using level contour reconstruction method

Direct numerical simulation of multiphase flow on fixed Eulerian grid became increasingly popular due to its simplicity and robustness. Some of the well-known methods include VOF, Level Set, Phase field, and Front Tracking method. Lately, hybridization of above methods gets its attention to overcome the disadvantages pertaining to each method. One hybrid approach developed by the author is the Level Contour Reconstruction Method (LCRM) which combines characteristics of both Front Tracking and Level Set method. Many engineering problems also contain complex geometry as boundary condition and proper representation of grid structure plays very important role for the successful outcomes. In this paper, an algorithm for handling arbitrary geometry inside fixed Eulerian computational domain with multiphase flow has been presented. Interface reconstruction between liquid and vapor phase has been performed outside of arbitrary solid boundary explicitly along with dynamic contact angle model. Sharp interface technique using ghost fluid point extrapolation method has been utilized for correct implementation of no-slip boundary condition at the wall. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Seungwon Shin received his B.S. and M.S. degree in Mechanical Engineering from Seoul National University, Korea, in 1995 and 1998, respectively. He then received his Ph.D. degree from Georgia Tech in 2002. Dr. Shin is currently a Professor at the School of Mechanical and System Design Engineering at Hongik University in Seoul, Korea. Dr. Shin’s research interests include computational fluid dynamics, multiphase flow, surface tension effect, phase change process.     

T型管流场混合多相流与欧拉多相流模型的数值研究

以计算流体动力学(CFD)的多相流数值计算理论及方法为基础,对处于复杂工况的T型管连接装置腔内流场进行了数值模拟分析,采用标准湍流模型和标准壁面函数对T型管接头内部流场进行了数值模拟;同时以混合模型求得的解作为用欧拉多相流模型的初始条件,采用欧拉多相湍流模型进行了对T型管接头内部流场数值计算.最后对两种模型计算得到的T型管接头内部流场的压力场、速度场及气相的体积分数(VOF)分布进行了对比分析.计算结果将指导的结构优化设计及失效分析.     

Dynamic imaging of multiphase flow through porous media using 4D cumulative reconstruction

This paper introduces an original application on reconstruction strategies for X‐ray computed microtomography, enabling the observation of time‐dependent changes that occur during multiphase flow. In general, by sparsely collecting radiographs, the reconstruction of the object is compromised. Optimizations can be achieved by combining specific characteristics of the dynamics with the acquisition. Herein, the proposed method relies on short random intervals in which no drastic changes occur in the sample to acquire as many radiographs as possible that constitute a reconstructible data set. As these intervals are unpredictable, the method tries to guarantee that the collected radiograph data during these specific intervals are enough to recover useful information about the dynamics. Simulations of a percolating fluid in a digital rock are used to replicate an X‐ray computed microtomography experiment to test the proposed method. The results demonstrate the potential of the proposed strategy for imaging multiphase flow in porous media and how data collected during distinct events can be combined to enhance the reconstruction of frames of the percolation process.     

Examination of disturbed pipe flow and its effects on flow measurement using orifice plates

In a great number of measurements the influence of a disturbed flow on the flow coefficient of a standard orifice plate was investigated. Single bends and double bends out of plane with and without spacer tubes were used as typical disturbances. Experiments were also performed using a combination with a star-shaped flow straightener. The necessary correction factors of the flow coefficient were determined for upstream straight length shorter than detailed in ISO 5167. The flow velocity profiles produced by the disturbances were examined and on this basis profile numbers were calculated. The examinations presented here show that the existing standard should be revised as regards the definition of the fully developed turbulent flow profile and the selection of the required upstream straight lengths.     

Performance model evaluation of turbine flow meter in vertical gas-liquid two-phase flows

Aiming at the need for flow measurement of gas-liquid flows in domestic gas well production, this paper proposes a measurement method based on the combination of the turbine flow meter (TFM) and a rotating electric field conductance sensor (REFCS). In experiments, the REFCS is used for the measurement of the gas holdup. To verify the applicability of the TFM models investigated in the previous study, for the modeling part, the mass, momentum and torque models are evaluated in vertical upward gas-liquid two-phase flows. In our model test, the meter factor model of TFM considers the effects of the slip ratio between the gas and liquid phases and flow patterns. In particular, the gas holdup involved in calculating the slip ratio in the model evaluation is obtained from the REFCS measurements. Model test results show the torque model has better volumetric flow rate prediction accuracy than the mass and momentum models. In the present study, the ranges of the liquid and gas phases are Q_w = 2–30 m³/d and Q_g = 1–16 m³/d, it was found that the average absolute deviation (AAD) in the predicted volume flow rate is equal to 1.23 m³/d and the average absolute percentage deviation (AAPD) is equal to 7.69%. The evaluated results presented in this paper will allow better estimates of the volumetric flow rates of gas-liquid flows based on the combined TMF and REFCS measurements during the monitoring of gas well production.     

Natural gas flow computer with open architecture using intelligent instrumentation and field bus

A new approach to natural gas flow computer design is presented in this paper. The developed system runs on a personal computer and employs the state-of-the-art mathematical models for corrections of some aspects of fluid flow dynamics, as well as for compressible behavior of gaseous fluid considerations. Orifice plates were used as primary elements. Measurements were performed through intelligent sensors. Results of the system metrological tests are also presented.     

超燃发动机流场组分浓度的在线测量

为了正确评价超燃发动机试验状态,采用自发拉曼散射技术在线测量了超燃发动机流场的主要组分。基于发动机试验条件和发动机与光学诊断技术的接口,建立了用于发动机流场组分测量的自发拉曼散射实验系统;测量了多车次发动机试验过程中流场主要组分的拉曼光谱;最后,通过光谱计算获得了流场主要组分浓度信息并重点分析了来流氧气含量及其变化情况。实验显示:发动机试验中,部分车次试验补氧后的来流中氧气的最大含量达到了30%,最小含量为18%,说明发动机试验过程中,对补氧量的控制精确和稳定性还有待提高。结果表明:采用自发拉曼散射技术可以较好地完成来流主要组分浓度测量工作,测量结果可用于发动机试验数据的分析及来流补氧控制方式和控制精度的改进。     

基于Fluent的调节阀内部流场数值模拟

建立了调节阀内部流场三维模型,采用通用CFD软件Fluent对其内部复杂流场进行了三维粘性数值模拟,通过对调节阀流量系数模拟值与理论值的比较,表明应用Fluent对调节阀进行模拟计算是可靠的,为调节阀结构改进提供了理论依据.     

Fluctuant pressure coefficient of the wake behind a bluff body in mist flow

Fluctuant pressure coefficient is presented as an index of vortex energy of the wake behind a bluff body in mist flow. Calculation for vortex energy is obtained from inter-phase force analysis, based on Basset-Boussinesq-Oseen equation and conservation of mechanical energy. Vortex energy is weakened by liquid disturbance, the relationship between the fluctuant pressure coefficient and liquid velocity is set up on theory analysis. An existence criterion for vortex streets is proposed using the relationship. A new algorithm for prediction of liquid velocity is put forward and compared with the method in Higham's patent. The predicted results fit the experimental results well.