Determination Of Measurement Uncertainty For The Purpose Of Wet Gas Hydrocarbon Allocation
Author(s): Per Lunde, Kjell-Eivind Frysa, Svein Neumann, Einar Halvorsen
Abstract/Introduction:
A Handbook of uncertainty calculations - Ultrasonic fiscal gas metering stations 1 has been developed in a cooperation between NFOGM, NPD and CMR, addressing fiscal metering of gas using multipath ultrasonic transit time flow meters (USM). The many different approaches to calculating the uncertainty of ultrasonic gas metering stations have been a source of confusion - varying practice in this respect has definitely been experienced. The intention of the present initiative has been that a handbook together with a spreadsheet program EMU - USM Fiscal Gas Metering Station, based upon the principles laid down in the Guide to the expression of uncertainty in measurement (GUM) 2 and ISO/DIS 5168 3, would satisfy the need for a modern method of uncertainty evaluation in the field of ultrasonic fiscal gas measurement. In the present work, calculation of the expanded uncertainty of the following four metering station measurands is addressed: the actual volume flow rate, the standard volume flow rate, the mass flow rate, and the energy flow rate.
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Document ID:
127FFCE8
Production Measurement Management
Author(s): Lex Scheers, Chris Wolff
Abstract/Introduction:
The production measurement process is more than just measurement hardware in the field but is the entire chain from data collection in the field up to the final production reporting. It includes all intermediate steps such as measurement and sampling guidelines, operational procedures, data processing (pVT), data transmission and reconciliation/allocation procedures. The customers of this measurement process are generally spread over several disciplines in the oil and gas companies and their partners or government bodies. Each of these customers has their own requirements regarding the measurement process. Production measurements have a vital economic impact on the business it not only costs money, but also delivers data that is used in decision-making processes such as production optimisation or reservoir modelling and in measuring the economic returns. Economics then not only set the uncertainty requirements for the production measurement process but often also indicate the most critical measurements. This could be oil flow rate, gas flow rate, watercut, GOR, gas volume fraction or even water flow rate in water-constrained facilities. As every field development has its own specific requirements for the production measurement process it will be demonstrated that a design phase and operations phase should be established. In the design phase the requirements from the customers are investigated and then compiled into a measurement philosophy and subsequently this results in detailed design and description of the system. Once production has started the measurement process should be managed through proper custodianship. The latter should be transparent and auditable and some organisational issues will be further discussed. In addition, with the more advanced measurement technology being installed in the field, such as multi-phase flow meters or modelling techniques, it becomes clear that proper management of this technology is essential in order to meet the customers expectations.
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Document ID:
28EBFD9E
Determination Of Measurement Uncertainty For The Purpose Of Wet Gas Hydrocarbon Allocation
Author(s): Robert A. Webb, Winsor Letton, Martin Basil
Abstract/Introduction:
The use of measurement uncertainty in the allocation of oil and gas is gaining interest in the industry. This so-called Uncertainty-Based-Allocation (UBA) utilizes the relative uncertainties of reference meters and allocation meters. The uncertainty of the allocation meters may differ significantly from one another and from the reference meters in both design and performance. The UBA approach attempts to use knowledge of meter uncertainty to equitably assign imbalance in the system. It has found immediate application in assigning the imbalance for wet gas systems in which one or all of the allocation meters is located subsea 1. While the mathematics used to perform Uncertainty-Based-Allocation is straightforward in its derivation and application, determination of the meter uncertainties that will be input to the calculations can be a formidable task. Not only are the systems that would use the approach often complex, but there are other problems which must be addressed as well. One is the determination of the uncertainty of each wet-gas meter at subsea flowing conditions. Another is the transformation of those uncertainties to the environmental conditions of the reference meter in order that the appropriate equations can be applied. Perhaps the most significant is the detection and allowance for systematic, or bias, errors in different parts of the system. Bias errors are particularly worrisome. After being effectively eliminated by calibration prior to system startup, they may gradually become significant in one or more meters during system operation over time, and be virtually undetectable without removal and test of the offending meter. Their effect is discussed further in Section 5.3. The effective combination of the Uncertainty-Based Allocation technique with the ability to determine meter and overall system uncertainty is of greatest value to the industry. The process has the potential to deal with difficult allocation situations and to open the door for incremental and marginal production, such as subsea tiebacks. The challenges which must be overcome in this process are not simple, however. Some of the most important will be discussed in what follows.
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Document ID:
37444FFC
Multiphase Flow Metering Per Well - Can It Be Justified?
Author(s): Lex Scheers, Khamis Busaidi, Mike Harper, Martin Halvorsen, Tor Wideroe
Abstract/Introduction:
Currently Multi-Phase Flow Meters (MPFMs) are developing from a nursing technology to mature technology and an increasing number of meters are being installed worldwide.
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Document ID:
2383DE81
Background And Operational Experience Of Multiphase Metering In The Safaniya Field- Offshore
Author(s): P. B. Warren, S. Hussain, S. Al-Ghamdi
Abstract/Introduction:
An automated and compact multiphase flow meter (MPFM) tested offshore Saudi Arabia has accurately measured three-phase flow rates under existing field operating flow conditions. An extensive eight-month field test in the Safaniya field was conducted from October 1999 to June 2000 utilizing over 350 well tests under varying operating conditions. A meter was installed on an offshore test barge, so that individual wells could be tested in series with traditional test barge methods. For these trial tests, the total liquid rate ranged from 1300 to 12000 barrels per day, the GOR ranged from 150 to 350 SCF/STB and the water cut ranged from 0 to 50%. The results indicate that over 90% of the wells tested were within +/- 10% of test barge results for both liquid and oil, and water cut (absolute) measurements. While gas measurements were determined to be within +/- 15% in 75% of the wells tested.
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Document ID:
C20D0FC8
Monetary Application For Multiphase Meters
Author(s): Jonathan Way, Ian Wood
Abstract/Introduction:
In 2001 Kerr-McGee (KMG) and its partners made the decision to develop the marginal Maclure and Tullich oil fields, by tying them back to the Gryphon Alpha FPSO. Both of the new fields have a markedly different ownership to the Gryphon field. Whilst there was a compelling requirement for accurate measurement of production between the three fields, it was similarly important to minimise Capex to ensure the developments were economically viable. Given this, multiphase metering was considered to allocate between the different ownerships, as opposed to traditional separator metering. The Maclure and Tullich fields first produced oil in July and August 2002 respectively. This paper discusses the multiphase meter selection criteria, installation, independent testing and the first three months of operation. The meters selected were the Framo/Schlumberger Phase Watcher (Vx) in two different sizes (52mm and 88mm). Independent flow tests, conducted at the U.K. National Engineering Laboratory and at ChevronTexacos Humble facilities demonstrated that an accuracy on the oil phase of 5% of reading could be achieved for typical gas volume fractions of 60 to 80% and water cuts less than 20%. Offshore the multiphase meters are verified against the test separator coriolis meters, these verifications reveal that the accuracy on the oil measurement is within the target range of 5% of reading.
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Document ID:
E3799C8D
Use Of Multiphase Meters In Process Control For Oil Field Well Testing: Novel Level Controls And Resulting Performance Enhancement
Author(s): Jack Marrelli, Ram Mohan
Abstract/Introduction:
First oil production from a deep water oil field is to be achieved by the installation of an Initial Development System (IDS). Well testing is required for field development and reservoir management. The well testing system requires high accuracy oil and water rates to provide the data needed for decision analysis in on going drilling programs. The well testing system must also be integrated with other platform operations such as well clean-up after drilling. We have simulated our concept of a certain type of multiphase meter in a feedback loop with conventional separation technology to extend the capabilities of both technologies. Concepts demonstrated here can also be easily applied as reto-fits to existing Separation Facilities which show accuracy or upset problems because of the simplicity and compact size of the additional multiphase meter component and non-disruptive supplementary integration with existing level control systems.
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Document ID:
F0933DC5
The Effect Of Varying Reynolds Number On A Zanker Flow Conditioner
Author(s): Neil Barton, Michael Reader-Harris, David Hodges, Craig Coull
Abstract/Introduction:
Perforated plate flow conditioners are widely used in the oil and gas sector to reduce swirl and flow asymmetry entering flow meters and hence improve their accuracy in non-ideal installations. These devices are typically developed and optimised in liquid (or low-pressure air) flow test facilities at relatively low Reynolds numbers. However, they are usually deployed in gas production metering systems that operate at higher Reynolds Numbers. This paper describes work in which the velocity profiles were measured downstream of a Zanker flow conditioner plate in swirling flow and asymmetrical flow in oil (at a Reynolds number of 2.5 x 105) and in nitrogen (at a Reynolds number of 5.8 x 106).
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Document ID:
F8CD84CC
CFD Analyses Of The Influence Of Flow Conditioners On Liquid Ultrasonic Flow Metering.
Author(s): Anders Hallanger
Abstract/Introduction:
Norsk Hydro experienced problems with an oil metering station consisting of two ultrasonic meters (USM 1 & 2) in series on the Oseberg Sr platform. Depending on the flow rates, the K-factor of USM 1 was outside the NPD requirements. USM 2, however, was inside the specifications. The problems could be caused by flow instability in USM 1. To investigate this a CFD study was carried out. Upstream of the meters was a flow conditioner (FC) in form of a seven-pipe tube bundle, and an asymmetric pipe contraction. The study revealed that the problems could be related to the tube bundle. The FC generated local jets after the pipes, and the distance from the FC to USM 1 was insufficient for proper mixing to take place. Different axial flow patterns were produced when the flow rate varied, giving unstable velocity profiles in USM 1. The CFD study was extended to look at the consequences of modifications to the flow line. Better results were obtained when the tube bundle was replaced with an Etoile (star) straightener, giving a more stable flow. Norsk Hydro has since then replaced the tube bundle with an Etoile FC, and recent results shows that both USM 1 and USM 2 will now satisfy the NPD requirements.
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Document ID:
A6BF544C
Benefits Derived From The Application Of Virtual Metering Production Simulation Software
Author(s): Bryan T. Yocum, Daniel Dunbar, Denis F. Pinto
Abstract/Introduction:
The original purpose of the client companies who sponsored our VSSM3 simulation technology research and development effort spanning several years was to provide a technical tool to optimize the design of the total integrated producing system, starting at the reservoir and flowing through to the terminal. While there are many sub- optimizations in the design of the equipment and producing facilities, there is an overall optimization. An important finding was that test separators did not have to be installed on offshore platforms, nor did they have to be installed in remote mountainous locations because the engineering software model technology could calculate the producing systems as accurately as non-engineered flow measurement. This reduced the size of platforms and eliminated the test lines. An important aspect of design optimization is the identification and avoidance of infeasible flow situations into future years due to such as slug flow, cease flow and increasing water cuts and gas fraction. This includes designing adequate and economic gravity and cyclonic gas-oil-water separation facilities to handle high viscosity emulsions and calculating gas oil separator liquid carry over and gas carry under effects.
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Document ID:
312CCA3B
Qualification Of Ultrasonic Flow Meters For Custody Transfer Of Natural Gas Using Atmospheric Air Calibration Facilities
Author(s): Jim Hill, Andreas Weber, Joern Weber
Abstract/Introduction:
The ability to operate in atmospheric air was a significant factor in the joint development by GE Panametrics and RMG Messtechnik of a custody transfer meter. Using air as a test medium yields major benefits. Two benefits are cost and availability. Natural gas calibration facilities cost thousands of dollars per day to use. This expense alone can accumulate into millions of dollars over the development of a meter, forming a barrier to entry to meter manufacturers. Also, the flow rate, if any, available at a natural gas test facility is dependent on seasonal, and even daily demand. The another factor is safety. Working at atmospheric pressure allows the developer to quickly make prototypes and design, without the safety concerns involved with high-pressure gas. Also, tests can be conducted with electronics exposed so that the performance of individual circuits and embedded software can be monitored, without the risk of encountering combustible gas. The final advantage is the flexibility that an open-loop calibration facility provides. Since the loop draws air from an open room, almost infinite combinations of installation conditions can be created. This is important, as actual field installations are a continuous distribution of configurations. Practical constraints limit the type of installations that can be simulated at a pressurized test facility. Combined, these factors lead to the conclusion that air operation was not merely desirable but in fact essential in order for our companies to develop and qualify a high accuracy meter.
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Document ID:
AEBE2E51
Operation Of Ultrasonic Flow Meters At Conditions Different Than Their Calibration
Author(s): William Freund, Klaus Zanker, Dale Goodson, James E. Hall, Andrew W. Jamieson
Abstract/Introduction:
Currently, calibration of an ultrasonic flow meter for natural gas measurement is conducted under the conditions available at the flow calibration facility. Since almost all of these facilities utilize natural gas flowing in a pipeline, it is usually not possible to vary parameters such as temperature, pressure and gas composition, each of which affect the speed of sound. When the ultrasonic meters are then used in applications where these parameters are different from their calibration values, does the calibration still apply? In order to quantify the effect of changes in these parameters on the calibration of ultrasonic meters, a series of carefully controlled calibrations have been performed.
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Document ID:
7338E611
Proving Of Multi-Path Liquid Ultrasonic Flowmeters
Author(s): T. Cousins, D. Augenstein
Abstract/Introduction:
For fiscal and custody transfer operation, statutory requirements and good practice have led to in-situ proving of liquid flowmeters. Proving has been used not only to remove the installation effects, but also to demonstrate the continuing performance of the meter. The characteristics of positive displacement meters and turbine meters have made in-situ volume proving both necessary and cost effective.
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Document ID:
B9D3C0F1
Analysis And Elimination Of Disturbing Flowrates Deviations Between A 24 Ansi 600 Ultrasonic Meter And Vortex Meter In A Natural Gas Meter Station
Author(s): A. Brmmer, H. Slawig, H. Jakel
Abstract/Introduction:
The VNG is operating an approx. 4.500 miles long pipe network for natural gas (Fig. 1) in the eastern part of Germany. One of the most significant stations of this network is the Steinitz gas transfer station which is located about 40 miles north of Magdeburg. Since its commencement of operation, the station is equipped with five measuring lines G4000 (max. 6.500 m/h where each line consists of a permanent series arrangement of turbine meter (TRZ) and vortex meter (WBZ).
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Document ID:
ECC7CD66
Evaluation Of Clamp-On Ultrasonic Gas Transit Time Flowmeters For Natural Gas Applications
Author(s): V. C. Ting, X. Shirley Ao
Abstract/Introduction:
This paper presents the results of meter performance tests of the Clamp-on Ultrasonic Gas Transit Time Flowmeter GC868 now manufactured by GE Panametrics. Evaluation tests were conducted during the week of December 3, 2001, at the Colorado Engineering Experiment Station, Inc., (CEESI) Wet Gas Test Facility in Nunn, Colorado, USA. The objective of these evaluation tests was to determine the accuracy of clamp-on gas flowmeters at field operating conditions where gas is dry and/or contains a small amount of entrained liquid. The clamp-on ultrasonic gas flowmeter was introduced commercially in 2001. Its transducers clamp on the outside of the pipe wall and cause no pressure drop despite wide rangeability. Since no tapping or cutting of the pipe wall is required, permanent installation costs are significantly reduced. Clamp-on ultrasonic gas meters are suitable for monitoring, control, and diagnostics applications. Advantages such as shorter tube length requirement, lighter meter weight, zero pressure drop, ease of installation and lower unit cost will contribute to capital expenditure (CAPEX) and operating expenditure (OPEX) reductions.
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Document ID:
D247112B
A New Ultrasonic Gas Flow Meter As A Base For A Natural Gas Energy System
Author(s): Toralf Dietz, Andreas Ehrlich, Volker Herrmann, Gnter Maurer, Burger Nath
Abstract/Introduction:
Ultrasonic technology has reached a high degree of maturity and is widely accepted throughout the measurement community. But there is still work to be done on technical and economical details until the technology will be as widely used as other technologies, e.g. turbine or orifice meters, and will have reached the predicted market shares 1 . Additional to the well-known volume flow measuring sites in gas transmission pipelines there is an upcoming need to measure natural gas energy content in remote, arbitrary locations. These are e.g. production fields or gathering lines. The paper describes an integrated energy measuring system for natural gas.
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Document ID:
0D822E17
Energy Flow And Wobbe Metering Based On Velocity Of Sound Measurements And Using A Corrective Techique
Author(s): H.J. Panneman, C.W. Koreman, S. Toonstra, F. Huijsmans
Abstract/Introduction:
Gasunie Research gained their years of experience in efficient energy utilization, gas measurement, and gas transport as the in-house laboratory for N.V. Nederlandse Gasunie. This company, which was an integrated gas transport and trading company until the beginning of 2002, has been one of the largest gas suppliers in Europe for several decades. As part of this company, Gasunie Research has always striven to guarantee the continuity of the gas supply, to ensure the safety of gas transport and to enhance the added value of natural gas as a fuel. Gasunie Research developed a wealth of new technology for domestic, commercial and industrial end users, and for the energy sector itself. The expertise that Gasunie Research has acquired through these activities and the years of practical experience is now made available to third parties.
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Document ID:
6419B0A4
New Compact Wet Gas Meter Based On A Microwave Water Detection Technique And Differential Pressure Flow Measurement
Author(s): ystein Lund B, Ebbe Nyfors, Tore Lland
Abstract/Introduction:
Future field developments will include wet gas or gascondensate fields with a very high GVF. In these cases, a test separator for well testing is often not a possible option and inline flow instruments will be requisite (see e.g. 1). The use of inline wet gas meters will be important to the field operators for well testing, continuous reservoir monitoring and production optimisation, allocation and flow assurance. The gas flow rate measurement is obviously a main focus of the wet gas metering technology because the gas value of the stream is dominating. This is however not the complete picture. In some gas-condensate fields, the value of the condensate production may be significant. It is moreover important to have a measure of the liquid components in the gas (condensate/water) for instrumental reasons, to improve the flow rate measurement accuracy.
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Document ID:
E2BF1CFF
Wet Gas Metering With V-Cone Meters
Author(s): David Stewart, David Hodges, Richard Steven, Rj W Peters
Abstract/Introduction:
Wet gas metering is becoming increasingly important in the development of marginal oil and gas fields. Many of these fields are only economically viable if they can be tied back to existing platform infrastructure, reducing the capital expenditure required by a significant margin. In these cases, several fields are often connected to common facilities, requiring each unprocessed stream to be metered before co-mingling. Wet gas metering can also be a valuable technology in well management, providing on-line information on the production flow and in well testing, reducing the capital expenditure required to investigate potential new wells.
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Document ID:
58BCD9DA
Field Installation Of Smartvent Wet Gas Flow Meters At Bintang,
Author(s): H. De Leeuw, B. Dybdahl
Abstract/Introduction:
Wet gas flow measurement is increasingly gaining acceptance in replacing expensive well test separators and related infrastructure by individual wet gas meters at each wellhead. At present more than 140 Petrotech wet gas meters have been purchased by various operators world wide. Besides the significant cost savings, the availability of continuous readings of each wells production rates allow for enhanced reservoir management and production optimisation. This paper presents a current overview of the application of wet gas flow measurement for the Bintang field developed by ExxonMobil. The Bintang development consists of permanently installed SmartVent wet gas venturi based flow meters at each well location.
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Document ID:
C9448D42
Investigation Of The Installation Effects On Ultrasonic Flowmeters And Evaluation Of Computational Fluid Dynamics Prediction Methods
Author(s): Craig J. Coull, Neil A. Barton
Abstract/Introduction:
This paper presents the results of a detailed investigation of installation effects on the performance of transit time ultrasonic flow meters. Extensive laboratory tests and Computational Fluid Dynamics (CFD) modelling have been performed. Laboratory tests have been carried out on a triple bend installation. Three meters have been tested two clamp-on meters (reflect diametric paths) and a dual-cross mid-radius meter. Each meters performance has been analysed and explanations offered as to why the observed effects occur. Path velocity data has also been recorded from the dual-cross midradius meter. This data has been used to reconstruct other mid-radius meter designs and allow their performance to be analysed. Also the diagnostic capabilities of individual path velocities in mid-radius design meters have been considered. The final section of the paper presents the results of the CFD modelling of the laboratory experiments. These results are analysed using the laboratory results including a pitot tube traverse of the test section.
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Document ID:
E2CBB824
Development Of A Diagnostics Tool For Gas Turbine Meters: The Acculert G - II
Author(s): Bertrand Reeb, Oliver Joachim
Abstract/Introduction:
Turbine meters are well known for their good metering abilities and repeatability, which accounts for their being the most widespread technology for custody transfer all over the world. In France only, 80% of all meters installed on the transmission network are turbines. These good performances are due to their principle of operation and to the choice of good quality mechanical elements, such as a well balanced rotor and bearings. Yet this can turn into a disadvantage, as turbine meters are fragile and can be damaged by solid particles in motion in the fluid, or even by a too severe pressurisation. With the current practice, the defaults inducing metrological errors (misreadings) can be detected only during periodic verifications, when the meter is dismounted and installed on a test bench. In France these verifications are planned every five years. Regularly a certain number of turbine meters is proved to be more or less severely misreading after this five year period. Both customers and gas companies are concerned by misreadings, and the need to improve the confidence in the meters accuracy and reliability is obvious. When it comes to monitoring solutions suited for turbine meters, some exist, like the spin test, but they are not very sensitive and none can avoid a costly and time-consuming dismounting of the meter. That is why the need for a practical and efficient tool for on-line monitoring of turbine meters was the starting point of an internal research program at Gaz de France.
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Document ID:
1BEEAE5F
Venturi Tubes: Improved Shape
Author(s): Michael Reader-Harris
Abstract/Introduction:
There is an increasing desire to use Venturi tubes for wet gas measurement, but to ensure accuracy in wet gas it is necessary to understand their behaviour in dry gas first. It was generally assumed until about seven years ago that the discharge coefficient at high Reynolds number in high-pressure gas would be constant and approximately equal to that obtained in water at Reynolds numbers greater than 2 105. However, work carried out at NEL reported by Jamieson et al 1, data reported by van Weers et al 2, and the papers on subsequent work at NEL 3-7 have shown that the performance of Venturi tubes in gas is very different from that in water. Some discharge coefficients in gas were greater than would have been expected by 3 per cent or even more. One factor which has an effect on how a Venturi tube performs is its internal shape. It is reasonable to consider the possibility that a profile with a smooth curve rather than sharp corners might be desirable. This paper therefore considers the performance of Venturi tubes of a range of profiles. Data were collected over the range of Reynolds numbers from about 105 to 107. The aim was to determine the best profile so that further work might provide a test of 4 Venturi tubes of the optimum profile.
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Document ID:
F65AC288
Recent Developments In The Uk Regulatory Regime
Author(s): Douglas Griffin
Abstract/Introduction:
The UK Department of Trade and Industry Guidelines have been completely restructured from the 1997 Issue 5. Issue 6 of the Guidelines was released for consultation in its final draft form in October 2001, and published officially in March 2002. For the first time the decision was taken to use industry experts to help formulate certain sections of the Guidelines. These contributions were then edited and compiled by the DTI. Approximately 60% of the Document was completed in this way - the remainder was drawn up entirely by the DTI. Each of the Modules of the Guidelines is intended to be, as far as possible, a stand-alone document. It is hoped that as a result its readership may extend beyond those with a direct interest in Fiscal Measurement. For example, reservoir engineers may find the Sections on Separator and Multiphase measurement of use, as their models may be based on measurements that use the techniques covered there.
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Document ID:
99C31387
Numerical Techniques For Uncertainty Modelling
Author(s): Michael Boyd
Abstract/Introduction:
This paper demonstrates two numerical techniques which can be used to calculate uncertainties more efficiently than using traditional analytical methods especially where the system being investigated is complicated. The techniques described are a Finite Difference method proposed in the ISO Guide to the Expression of Uncertainty in Measurement 1, followed by an introduction to Monte Carlo modelling. Algorithms for converting conventional computer random number generators into those required for other distribution types are provided in the Appendix. A simple spreadsheet macro is described that will allow users to build an interface for creating dynamic uncertainty models for even the most complicated systems. The method described allows users to calculate uncertainties for any system using a simple point and click interface that requires little statistical expertise.
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Document ID:
2D0FED3B