4.1 functional design specification (fds)

Functional description Document no. / rev.: 091980 / E

Roxar Multiphase meter 2600

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Roxar Template doc. no. / rev.: 034708/D

Functional description for Roxar Multiphase meter 2600



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TABLE OF CONTENTS

1. Purpose........................................................................................................................................... 3 2. Abbreviations / Definitions ............................................................................................................ 3

2.1 Abbreviations ............................................................................................................................. 3 2.2 Definitions .................................................................................................................................. 3

3. Revision history ............................................................................................................................. 5 4. Documentation ............................................................................................................................... 5

4.1 Standard documentation and records ........................................................................................ 5 4.2 Location and precautions ........................................................................................................... 5 4.3 Storage time .............................................................................................................................. 5

5. Introduction .................................................................................................................................... 6 6. System overview ............................................................................................................................ 7

6.1 Meter body ................................................................................................................................. 7 6.2 Replaceable insert Venturi ......................................................................................................... 8 6.3 Multivariable transmitter (P, DP, T) ............................................................................................ 8 6.4 Isolation block and bleed valve .................................................................................................. 8 6.5 DP26 electrode sensor geometry .............................................................................................. 9 6.6 Impedance field electronics ....................................................................................................... 9 6.7 Gamma densitometer (if applicable) .......................................................................................... 9 6.8 Junction box ............................................................................................................................ 10 6.9 Flow computer enclosure ......................................................................................................... 10 6.10 PC 104 flow computer ............................................................................................................. 10 6.11 Service console ....................................................................................................................... 10

7. Functional overview ..................................................................................................................... 11 7.1 Meter body ............................................................................................................................... 11 7.2 Replaceable Venturi, MVT and Parker-Isolation valve ............................................................. 11 7.3 DP26 electrodes with impedance field electronics ................................................................... 12 7.4 Gamma densitometer system (mini-gamma version) ............................................................... 13 7.5 Flow computer enclosure ......................................................................................................... 14 7.6 Service console (HMI).............................................................................................................. 15

8. Principle of operation .................................................................................................................. 16 8.1 Fraction measurement ............................................................................................................. 17 8.2 Velocity measurement ............................................................................................................. 21 8.3 Reference data need ............................................................................................................... 24

9. Wetgas mode ................................................................................................................................ 25 10. System performance and characteristics .................................................................................. 27

10.1 Standard specification ............................................................................................................. 27 10.2 Operating range ....................................................................................................................... 28 10.3 Measurement uncertainty ........................................................................................................ 29



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1. PURPOSE The purpose of the functional description document is to help the user to understand what multiphase metering is and how the Roxar Multiphase meter 2600 operates. This document is a technical description in which are described all major Roxar Multiphase meter 2600 components and how they function together, and explains the principle of operation and how the ZectorTM platform is used to provide the volumetric flow rates of oil, water, and gas.

2. ABBREVIATIONS / DEFINITIONS

2.1 Abbreviations AGC Automatic Gain Control MW Mole weight GOR Gas oil ratio PEEK Polyetheretherketone GVF Gas volume fraction PVT Pressure, volume, and

temperature SCADA Supervisory Control and Data Acquisition HMI Human machine interface SG Specific gravity Roxar MPFM 2600 Roxar Multiphase meter 2600 WC Watercut MVT Multivariable transmitter WLR Water liquid ratio WVF Water volume fraction PVTx PVT simulating software NFOGM Norsk Forening for Olje og Gassmåling DCS Distributed control system rel % Relative uncertainties in gas and liquid

flow rate abs % Absolute uncertainty for water in

liquid ratio GVF Gas volume fraction WTr Transition point oil/water -

continuous liquid phase VLR Vapour liquid ratio RTD Resistance temperature detector

2.2 Definitions · Flow regime – The physical geometry exhibited by a multiphase flow in a conduit; for

example, in two-phase oil/water, free water occupying the bottom of conduit with oil or oil/water mixture flowing above.

· Gas oil ratio – The ratio of gas volume flow rate and the oil volume flow rate; both volume flow rates should be converted to the same pressure and temperature (generally at standard conditions). Expressed in a volume per volume, e.g. scft/bbl or m3/m3.

· Gas volume fraction –The gas volume flow rate, relative to the total multiphase volume flow rate, at the pressure and temperature prevailing in that section. The GVF is normally expressed as a fraction or percentage.

· Mass flow rate – The mass of fluid flowing through the cross-section of a conduit in unit time.

· Capacitance – In a capacitor or system of conductors and dielectrics, the property that permits the storage of electrically separated charges when potential differences exist between the conductors. Capacitance is related to charge and voltage as follows: C = Q/V, where C is the capacitance in farads, Q is the charge in coulombs, and V is the voltage in volts.

· Conductivity – The ability of a material to conduct electrical current. In isotropic materials the reciprocal of resistivity. Sometimes called specific conductance. Units are Siemens/m or S/m.



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· Permittivity – The permittivity of a dielectric medium is a measure of its ability to be electrically polarized when exposed to an electrical field. A dielectric medium in a condenser will, due to the polarization, decrease the original electric field and increase the capacitance of the condenser. The capacitance C of an electrical condenser is proportional to the permittivity of the dielectric medium. (ref: NFOGM Handbook of Multiphase flow metering [2] for more details)

· Impedance – Electrical impedance, or simply impedance, describes a measure of opposition to a sinusoidal alternating current (AC). Electrical impedance extends the concept of resistance to AC circuits, describing not only the relative amplitudes of the voltage and current, but also the relative phases. When the circuit is driven with direct current (DC) there is no distinction between impedance and resistance; the latter can be thought of as impedance with zero phase angle. The symbol for impedance is usually Z and it may be represented by writing its magnitude and phase in the form qÐZ

· Measuring envelope – The area's in the two-phase flow map and the composition map in which the Roxar MPFM 2600 performs according to its specifications.

· Multiphase flow – Two or more phases flowing simultaneously in a closed conduit of oil, water and gas in the entire region of 0-100% GVF and 0-100% water cut.

· Oil-continuous flow – A multiphase flow with a oil/water mixture characterized in that the water is distributed as water droplets surrounded by oil. Electrically, the mixture acts as an insulator.

· Standard or reference conditions – A set of standard (or reference) conditions, in terms of pressure and temperature, at which fluid properties or volume flow rates are expressed, e.g. 101.325kPa and 15°C.

· Superficial phase velocity – The flow velocity of one phase of a multiphase flow, assuming that the phase occupies the whole conduit by itself. It may also be defined by the relationship (phase volume flow rate) / (pipe cross-section).

· Water-continuous two-phase flow – A two-phase flow of oil/water characterised in that the oil is distributed as oil droplets surrounded by water. Electrically, the mixture acts as a conductor.

· Water cut – The water volume flow rate, relative to the total liquid volume flow rate (oil and water), both converted to volumes at standard pressure and temperature. The WC is normally expressed as a percentage.

· Water liquid ratio – The water volume flow rate, relative to the total liquid volume flow rate (oil and water), at the pressure and temperature prevailing in that section.

· Repeatability – Closeness of the agreement between the results of successive measurements of the same measurand carried out under the same conditions of measurement.



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3. REVISION HISTORY Revision Description

A New Customer Documentation B Adding info and adjust wording C Updating into new template. Added new abbreviations. Updated chapter 2, 6 to 9. Added chapter 1. D Updated chapter 10.3, to include measurement uncertainty for the Wetgas mode. E Updated chapter 8, 8.2.2 – Venturi velocity and chapter 10.3.1 – Measurement uncertainty for the

Roxar 2600 MPFM Multiphase mode.

4. DOCUMENTATION

4.1 Standard documentation and records Document name Type Doc. Reference [1] Operating instructions Instructions TCE – 091983 [2] NFOGM Handbook of Multiphase Flow Metering www.nfogm.no Manual –

4.2 Location and precautions Doc. level: 4. Document Classification: Open. All records from this process shall be stored in the document system under relevant folder.

4.3 Storage time The records shall be stored during the products life time or as specified in the clients’ contract, a minimum of 20 years is required. Note: If the client requires notification before records are discarded, this must be stated on the record itself.

http://www.nfogm.no/



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5. INTRODUCTION Roxar Multiphase flow meter 2600 is Roxar’s third generation meter built on the ZectorTM Technology platform that includes upgraded non-Gamma algorithms, wetgas algorithms, advanced signal processing, compact sensor geometry, and impedance field electronics. The Roxar MPFM 2600 is an inline, non-intrusive meter that measures multiphase flow without separation or mixing.

Figure 1 Roxar MPFM 2600 standard version (Non-Gamma)

In multiphase metering the goal is to find the volume of each phase of each fluid-component in a multiphase mixture; volume of oil, water and gas. If a confined area is given then the volume flow rate will be given by the area multiplied with the velocity. This statement is also true considering the same for each phase. So the principle equation that needs to be solved to find the volume of each phase is: Q(phase) = A(phase) * V(phase) Q(phase) = Volumetric flow of a phase A(phase) = The area occupied by a phase V(phase) = The velocity of a phase This document is describing how Roxar is using the ZectorTM Technology platform in the Roxar MPFM 2600 and its components and principle to measure multiphase flow. The functional description document for the Roxar MPFM 2600, including the principle of operation chapter, is kept to a level that will help the user to understand how the meter function and operates, without exploring all details.



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6. SYSTEM OVERVIEW In this chapter an overview of the basic characteristic and mechanical design of all major components are explained. How these components function together and are used to measure are discussed in more detail in the chapters hereafter. All individual parts of the Roxar MPFM 2600 are shown in Figure 2. They are shown together as a complete Roxar MPFM 2600 system in a block diagram presentation to make it easier to relate to the explanation of each individual component.

Figure 2 Block diagram of the Roxar MPFM 2600.

6.1 Meter body

Figure 3

The Roxar MPFM 2600 has a compact, light-weight design that has effectively reduced 80% of the weight and half the length compared to the second generation of multiphase meters from Roxar. The meter design has a protective frame around the main components such as the MVT and the impedance field electronics enclosure, which also functions as a sun shade. The meter body is designed with Graylock/Tecklock hubs.



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6.2 Replaceable insert Venturi

Figure 4

The Roxar MPFM 2600 has a sleeve design Venturi that allows for an easy replacement in the field when required. The Venturi DP tapping has no instrument tubes, but has the proved design with ring-room chamber pressure tapping to give both pressure and DP. For functional overview, please see section 7.2

6.3 Multivariable transmitter (P, DP, T)

Figure 5

The Roxar MPFM 2600’s pressure, differential pressure (DP) and temperature measurements are provided by a compact, integrated solution using an Emerson Rosemount multivariable transmitter 3095-MA. For functional overview, please see section 7.2

6.4 Isolation block and bleed valve

Figure 6

Parker double-block-and-bleed valve for process isolation. For functional overview, please see section 7.2



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6.5 DP26 electrode sensor geometry The DP26 electrode sensor geometry is a patented design for the Roxar MPFM 2600. There are 2 electrodes in the downstream level and 6 electrodes in the upstream level, hence DP26 electrode sensor geometry. For functional overview please see section 7.3

Figure 7

6.6 Impedance field electronics This impedance field electronics is the electrical unit that is connected to the DP26 electrodes with ultra high speed direct processing and data verification. For functional overview, please see section 7.3

Figure 8

6.7 Gamma densitometer (if applicable)

Figure 9

The mini-gamma system is used to measure the mixture density of the fluid flowing in the Roxar MPFM 2600 section. The gamma system can easily be retrofitted to a non-gamma version of the meter in field post-commissioning, if the flow conditions dictate so. For functional overview, please see section 7.4



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6.8 Junction box

Figure 10

A junction box in hazardous area may be used if the distance between the meter body and the flow computer enclosure is requested to be more than 10 metres due to application requirements (see Figure 2).

6.9 Flow computer enclosure

Figure 11

The flow computer enclosure that contains the Meter’s calculation processing unit may be supplied in different classifications such as:

· EEx d enclosure with local display · Safe area enclosure · 19” rack mountable front- and back plate

(see section 6.10, 7.5 and Figure 2)

6.10 PC 104 flow computer

Figure 12

The Roxar MPFM 2600 has a PC104 flow computer which is the calculating unit that performs all high speed calculations of flow algorithms and also communicates with all internal instrumentation, service console and client systems. It is located inside the flow computer enclosure.

6.11 Service console

Figure 13

Service console laptop/ PC with installed HMI (human machine interface, Figure 13) Roxar MPFM 2600 Service console software installed on a standard laptop or PC running on windows (XP or Win 2000). An industrial PC type may be supplied for cabinets or similar solutions.



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7. FUNCTIONAL OVERVIEW This chapter is combining the parts described in the previous chapter and relates them to their function in the whole system.

7.1 Meter body The Roxar MPFM 2600 is as mentioned smaller and lighter compared to the second generation. It is still a full bore non-intrusive multiphase meter and contains all instrumentation to perform all necessary measurements. The Meter body is equipped with standard hub flanges for interfacing to the adjacent piping and this is the only available interface delivered on the meter body itself. To install the Meter to other flange types, Roxar can deliver crossovers spools if required.

7.2 Replaceable Venturi, MVT and Parker-Isolation valve

7.2.1 Venturi The Roxar MPFM 2600 has an insert sleeve design Venturi that allows for an easy replacement in the field if required. The Venturi (DP) tapping has no instrument tubes, but has a ring-room chamber pressure tappings for both line-pressure and differential pressure (DP). The DP is the main input to calculate the liquid velocity (see Figure 14).

Figure 14 By replacing the existing Venturi sleeve with a new one (with a different beta-ratio) the actual operating envelope of the existing Roxar MPFM 2600 will increase. Replacing the Venturi can be done as an on-site operation. By removing the downstream bend of the Roxar MPFM 2600 and allocate space above the Meter it is possible to pull the Venturi section out of the meter body after the locking mechanisms have been removed. A new Venturi unit with a smaller or larger Venturi throat can then be inserted back into the meter body. Possible scenarios where a replacement could be considered:

· Customer can order a spare Venturi kit based to extend the operating range and use the same Roxar MPFM 2600 for the entire life time of a well.

· If actual well production is not coherent with the initial design process data, one solution could be to replace the existing Venturi (beta ratio x) with a more suitable and optimal size (beta ratio y).



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7.2.2 Isolation valve To keep the pressure integrity from the process to the transmitter, Roxar is using a Parker block and bleed isolation valve from the PARKER CCIMS family. This is a compact solution and has a flanged connection between the Roxar MPFM 2600 body and the valve (see Figure 15).

Figure 15

7.2.3 Multivariable transmitter To transmit present line pressure and DP to the PC104 flow computer for further processing, Roxar MPFM 2600 utilizes an Emerson-Rosemount 3059-MA that enables highly accurate pressure measurements, in combination with extremely good long term stability. Additionally to the pressure and DP a temperature element is connected to the MVT to provide the flow temperature to the systems algorithms. This internal RTD (Resistance temperature detector) element is a part of the sensor design. The actual pressure and temperature is used to calculate the reference properties for each phase at actual condition and also to calculate the conversion factors to convert from actual flow rates to standard flow rates.

7.3 DP26 electrodes with impedance field electronics Phase fractions measurement of gas, oil and water and the gas velocity are measured by impedance field electronics. The Roxar MPFM 2600 is in a one card solution combining a capacitive mode and a conductance mode of the impedance measurement. The DP26 electrodes are wetted parts of the Roxar MPFM 2600 electrical measurement and the standard material used for these electrodes is Inconel to ensure the material integrity regardless of process condition. The electrodes are electrically isolated from the meter body by using a PEEK liner.



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Figure 16

The electrodes are wetted parts and are also used to excitation and detection of signals to determine the variation of the electrical properties in the multiphase flow. Signal variations detected on these electrodes are in addition used in cross correlation algorithms that determine the gas velocity. The signals generated by the electrodes are also used for advanced signal processing used when the meter operates in non-Gamma modus to determine the gas- and liquid fractions.

The DP26 electrode mechanical design has no internal wires or soldering points from process to atmosphere. Each electrode bolt has a pressure barrier design. These bolts are connected with wires to a common impedance electronic board and this allows for seamless switching between capacitive mode and conductance mode when the flow changes from oil to water – continuous and vice versa (see Figure 16). DP26 electrode geometry allows for measurements in separate sectors in addition to the full cross sectional area. This introduce the possibility to measure a large number of different combinations with near-wall-measurement, rotational measurement and traditional bulk-measurement, enabling a significant more detailed fraction measurement. The principle of the impedance method for phase fraction measurements is used to characterize the electrical properties of the fluid passing through the sensor. By measuring the electrical impedance using the contact electrodes; the fluid mixture permittivity and fluid mixture conductivity are found and through advanced signal processing and verification each phase fraction and velocity is determined.

Figure 17

The capacitance mode is mainly active when the fluid mixture is in oil-continuous state, meaning the fluid mixture acts as an electrical insulator. The conductance mode is mainly active when the fluid mixture is in water-continuous state, meaning the fluid mixture acts as an electrical conductor. The switching between these two modes is as mentioned above seamless, fully automatic and occurs at extremely high speed. The two different levels in the electrode configuration allows for cross correlation of the electrical signals from the upstream to the downstream level. By performing a statistical cross-correlation method, the velocity of the gas flow is found. This will be discussed in more detail in section 8 - Principle of operation (see Figure 17).

7.4 Gamma densitometer system (mini-gamma version) Roxar requires the gamma densitometer system to be used for special applications or when GVF is high and when the liquid phase becomes insignificant to the flow volume of gas.

The gamma densitometer system measures the density of the mixture flowing in the pipe based on a calibration with two known mediums, typically gas and water. In Figure 18 a visualization of the two main components of the gamma densitometer system are shown,



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the detector including the coherent EEx d enclosure and the gamma source.

Figure 18

The gamma-ray attenuation technique is based on the principle that due to absorption, intensity of a gamma beam decreases exponentially as it passes through matter. The gamma densitometer is measuring the mixture density and the result is utilized to determine the gas/liquid split. The gamma detector used is a standard T205 detector bolted on to the outside of the meter body (see Figure 18).

The radioactive source is isotope Cesium 137 (Cs 137), and the source container has an IP 68 protection with a dose rate of less than 7.5m Sieverts per hour on any accessible surface. Provided instructions and regulations are followed, the Gamma densitometer is completely safe and does not pose any form of danger. Non-gamma solution In low to medium gas volume fractions the Roxar MPFM 2600 does not need a gamma densitometer to measure the split between gas and liquid. In those cases the split ratio is found by using patented advanced signal processing algorithms. This will be discussed more in section 8.

7.5 Flow computer enclosure The flow computer enclosure may be supplied in different classifications as seen in section 6.9, but regardless of which solution that is chosen the following part will be included:

· PC 104 flow computer (calculating unit) · Barriers for transmitter and field electronics · Converters for different communication-interfaces · Power conditioning modules · Local display unit (Ex-d Enclosure only)

Through a dedicated communication port all data described in the Modbus address mapping are made available to a third party client systems such as SCADA, DCS etc. The flow computer includes 6 communication ports using different interface where 4 ports are for internal communication only and where 2 are used to communicate with the service console and any client communication: COM (dedicated client port) and COM6 (service port). The display unit controlled by the push-button panel is installed in the front door of the EExd enclosure. The display shows flow rates, primary parameters, totalized flow rates and well test operations. Push-buttons have a navigation/select function used to toggle between the display modes as well as for well test setup.



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7.6 Service console (HMI) The meter is commissioned and serviced using a menu based configuration and monitoring software tool installed in the service console PC. The software may be used in order to carry out the following tasks: · Download new PVT data sets to the meter · Select PVT data set to be used for current logging · Configure the meter data, like engineering units and data averaging properties · Trend and display real time measurements · Log instantaneous and accumulated data, either as text files or as an excel DDE exchange format.

Text files can be imported into standard spread sheets like excel or lotus (not included) · Generate log files containing time stamped process alarms and technical alarms · Define passwords for users · Run well tests

7.6.1 Data logging and storage back up During normal operations or well testing when the Roxar MPFM 2600 HMI is used (Service console connected to the flow computer) the following files are stored at the laptop/PC where the service console is installed: modifications_1.txt: Log files containing modifications action s made from the service console software ProcessLog_1.txt: Log files containing any process related alarms TechnicalLog_1.txt: Log files containing any technical alarms yy_mm_dd_A001.log: Log files with selectable parameters chosen in the service console, such as flow rates, density etc. yyyy-mm-dd_0.rep: Well test report in a txt-format yyyy-mm-dd_0.bmp: Print-screen automatically generated of the well test panel. When a laptop/PC is not connected, it is obvious that no files are stored at the laptop but a similar file as the yy_mm_dd_A001.log is stored at the flow computers internal memory as a backup. This file is named yy_mm_dd_A240.buf This back up file is available up to several years back depending on the amount of parameters logged and the interval. Typical parameters would be oil, water and gas rate with the prevailing pressure and temperature, etc. (see ‘Operating instructions’ [1] for more details). The service console is used for the tasks mentioned above but is not an absolute requirement to have installed to operate the Roxar MPFM 2600. Most of the daily operations can be controlled by a DCS, SCADA system using read/write commands to the PC104FC. For more details about the Roxar MPFM 2600 HMI kindly refer to Operating instructions [1].



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8. PRINCIPLE OF OPERATION The object of this chapter is to explain the principle of operations and how the ZectorTM technology platform is used to provide the volumetric flow rates of oil, water and gas. The flow diagram below is a schematic explanation of how the signal floats through the Roxar MPFM 2600 from the hardware through the flow computer algorithms to the final output: volumetric flow rates.

Figure 19



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Roxar MPFM 2600 is based on a ZectorTM Technology platform which consists of advanced and patented signal processing, dual plane 2-6 electrode geometry where signals are processed by impedance field electronics. This technology platform allows for a more complex and more correct modelling of the multiphase flow. ZectorTM Technology uses a multi-velocity system which handles asymmetrical bubble shapes, and less-than-perfect mixture of the dispersed phase. As mentioned in the very beginning of this document the main equation to solve within the trade of multiphase metering is:

vAQ ×= Q = Volumetric flow rate A = Area of pipe cross section v = Flow velocity In order to determine the volume flow of oil, water and gas, the velocity of each phase must be measured as well as the fraction of each phase in the pipe void. The superior equation combination that must be solved and gives the fractions of each phase is as follows: Oil-continuous flow: equations 1, 3 and 4 Water-continuous flow: equations 2, 3 and 4 Permittivity: 1) ),,( oilwatergasmixture f gebeaee =

Conductivity: 2) ),,( oilwatergasmixture f gsbsass =

Density: 3) ),,( oilwatergasmixture f grbrarr = Combined: 4) 1=++ gba Where: =a gas fraction

=b water fraction =g oil fraction

In chapter 8.1 it is explained how Roxar use the technology platform to determine the fraction of each phase and in chapter 8.2 the velocity measurement is discussed.

8.1 Fraction measurement The Roxar MPFM 2600 impedance measurement has mainly a capacitive component in oil-continuous flow and mainly a conductive component in water-continuous flow state; hence a capacitive mode and conductance mode.



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8.1.1 Capacitance mode The capacitance mode of the impedance measurement of the Roxar MPFM 2600 measures the capacitance in the pipe void which is related to the permittivity of the oil/gas/water mixture. Permittivity is another term for the dielectric constant of a matter. (Reference: NFOGM Handbook of multiphase flow metering [2]) The permittivity for hydrocarbons is very different from water as seen in Figure 20, and the measured permittivity of the mixture is therefore a measure used to split the hydrocarbon and water. Natural gas and air have a permittivity close to 1, oil has a typical span from 2.0 – 2.4. The water permittivity as seen in the figure is at the other end of the scale with approximately 70. This provides the Roxar MPFM 2600 with a measurement principle that is extremely sensitive to changes in the water fraction and it is not affected by changes in the salinity of the water. By using contact electrodes on the inside of the spool that are in direct contact with the multiphase flow, the detection of the generated signal will vary depending on the mixture permittivity which again is a result of variations in the ratio between oil, gas and water.

Figure 20

Figure 21

The variations in the measured capacitance hence mixture permittivity are displayed in Figure 21. It is clear that the water fraction will make the measured capacitance/permittivity value increase and an increase in gas fraction in the conduit will decrease the measured value. By combining the mixture density measurements from the Gamma density system to determine the gas fraction and the capacitance measurements in oil-continuous flow, the oil fraction, water fraction and gas fraction are known.



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8.1.1.1 ZectorTM technology platform

Figure 22

The Roxar MPFM 2600 has as earlier described 2 different levels or planes with electrodes. The downstream plane has two electrodes and is measuring the bulk void electrical properties. It is also a part of the cross-correlation configuration. But as a result of the electrode configuration with 6 electrodes in the upstream electrode level and the new impedance electronics the Roxar MPFM 2600 is capable of providing a comprehensive mapping of the flow regimes.

The meter is not only using the classic cross sectional measurements as seen in Figure 22, but also rotational near wall measurements and cross-volume measurements per section, thereby providing a comprehensive mapping of the flow regimes. This is indicated in Figure 23 – Asymmetrical flow and less-than-perfect mixtures of the gas and the dispersed phase can be handled in a manner that earlier was not possible.

Figure 23 The Zector technology allows for an accurate understanding of flow regimes, mixing effects and velocity profiles. It can detect rapid changes in phase splits, and thereby making the measurements even more accurate and consistent. The Zector technology measures multiple liquid and gas flow velocities - for example near wall velocity will be different to centre of pipe velocity. Velocities will also vary over time, due to composition, turbulence, viscosity and other effects.

This technology also allows for a large number of simultaneous sectors of the flow to be investigated with a measurement rate of 12,000 measurements per second, giving unparalleled possibilities for interpretation.



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8.1.2 Mode switching As long as the flow is in oil-continuous state the measured impedance will contain mainly a capacitance component and the conductance component will be negligible. Normally, the flow will stay in oil-continuous state as long as the water cut is below approximately 60 – 70%, but there would be large application variation in that threshold. For high water cuts, typically above 70%, the capacitance component will decrease and the conductance component will increase and subsequently for water continuous flow. The measured impedance will have mainly conductance components as explained in chapter 8.1.3. Which mode to operate in is determined by a resistance measurement to find the conductance of the multiphase mixture in the conduit, that again is converted into an AGC-voltage that provides the flow computer with an input to change or not.

8.1.3 Conductance mode In conductance mode the mixture conductivity is measured. Conductivity is the measure of the ability of a solution to conduct electric current. It is the reciprocal of electrical resistivity (Conductivity = 1/R). The impedance measurements in capacitive mode is not suitable when the multiphase flow is in water-continuous state and for this reason the conductance mode is used to determine the water fraction of the mixture. Similar to the capacitance mode in oil-continuous flow the conductance mode finds the water fraction of the water-continuous mixture. By combining the known water fraction along with the gas/liquid split found from either patented non-gamma algorithms or the gamma densitometer system oil fraction, water fraction and gas fraction are known (see Figure 24).

The conductivity is measured by injecting a known electrical current by contact electrode into the flow, and then measure the voltage drop between electrodes along an insulated section of the pipe. By measuring both the current and the voltage drop, the resistance is calculated using Ohm’s law and hence the mix conductivity. Furthermore, whereas contact electrodes have traditionally suffered from variable surface resistance, this is overcome by the Roxar MPFM 2600 DP26 design by using 4 of the 6 electrodes in the upstream electrode geometry for conductivity measurement.

Figure 24



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8.1.4 Gamma densitometer system Density The gamma-ray attenuation technique is based on the principle that due to absorption, intensity of a gamma beam decreases exponentially as it passes through matter.

Figure 25 The variation in density for a multiphase flow is shown in the principle sketch in Figure 25. The solid lines show how the density will vary with the gas fraction going from 0 to 100% when the water cut in the liquid is kept constant from left to right. The lower solid line shows the course for water cut = 0%. The arrow shows the influence of increasing water cut up to 100% for the upper solid line; i.e. the higher the WC, the higher the flow density.

8.2 Velocity measurement Roxar MPFM 2600 has two different methods for flow velocity measurement:

· Cross-correlation of time series signals from the impedance sensor to determine the gas velocities.

· DP measurement over Venturi meter to determine the liquid velocity.

0 0 % 100 %

Gas Volume Fraction

Flow density

Increasing water cut WC = 100%

WC = 0%

Water density

Oil density

Gas density



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8.2.1 Cross – correlation velocity measurement Impedance field electronics collect data points from the sensor electrodes at a rate of approximately 1 million times pr. second. The collected data forms a time serial signal and contains information about the flow pattern inside the meter.

Figure 26

The distance d between the two electrode planes is known. In plot in Figure 26, the time series signals from the two electrodes are plotted. The signal from the upstream electrodes is the brown curve; the signal from the downstream electrodes is the green curve. The curves have almost the same shape but are shifted in time.

The statistical method cross-correlation compares the similarities between the signals and is used to find the time shift. The cross correlation function versus time returns its first and highest maximum at a time T representing the time shift between the signals. The velocity is then found as: Vflow = d/T Where: Vflow = Flow velocity d = Distance between the electrodes in an electrode pair T = Time shift found by cross-correlation of time series



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The Roxar MPFM 2600 has, as mentioned, two electrode planes, one with 2 and one with 6 electrodes, which during the main cross-correlation and signal processing measures the raw gas velocities. The upstream level of electrodes is utilizing 4 electrodes to ensure cross correlation between level 1 and 2. The electrical field for the upstream level with 6 electrodes during cross correlation is indicated in Figure 27.

Figure 27

8.2.2 Venturi velocity The DP across a Venturi is proportional to the kinetic energy of a mixture passing through. Thus, the response curve of a Venturi meter is related to the mass of the mixture and its velocity. The starting point for the application of the Venturi is the general Venturi equation derived from Bernoulli’s equation.

rp )(2

421

22 ppDCeEQ -

=

Q = volumetric flow rate

2D = diameter of the throat (meter specific ID)

1D = diameter of the Venturi meter entrance (meter specific ID) C = the discharge coefficient e = expansibility factor

E = 4

1

21

1

÷÷ø

öççè

æ-

DD

(Beta-factor input)

ρ = the density of the medium generating the DP, mix density )( 21 pp - = the differential pressure (DP) measured by the differential pressure sensor

K = collective of constants V = Venturi Velocity If all constants are collected in the K factor and the expression is divided by the area the expression may be simplified to:

rPKV D

=

In the Roxar MPFM 2600 the general Venturi equation is modified for use in three-phase flow. The modified equation takes into account the gas volume fraction (GVF) of the flow. Since the mixture density is measured with the gamma densitometer or from the non-gamma versions algorithms the liquid velocity can be determined from the measured DP.



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8.3 Reference data need The input parameters to the Roxar MPFM 2600 are data such as reference oil, water and gas densities at the prevailing pressure and temperature conditions, as well as oil permittivity and water salinity. This data is used directly in the algorithms to calculate the actual volume flow rates and are provided to the flow computer in one out of two methods, either a black oil model or a density-table generated by a PVT-simulating program such as Tempest PVTx or similar program. The black oil model is not recommended to use unless strictly necessary. PVT-simulating programs use a HC fluid composition analysis with the desired Equation of State and a coherent standard property library to simulate the fluid behaviour as a function of pressure and temperature. The results are provided in a matrix that the flow computer use to calculate the correct phase density of oil, water and gas automatically as the line conditions change. The same PVT-simulating program will generate another matrix that will automatically provide the flow computer with the correct conversion factors for the oil, water and gas from actual line condition to standard condition. Input data to the Roxar Tempest PVTx Programme are: · Compositional fluid analysis with a mole% plus fraction (Cn+) including coherent values of MW and

SG. · The water salinity/conductivity (if flow is in water continuous state) and water density.

Any results from lab PVT-experiment will also contribute to ensuring optimal quality of the table input. For more details kindly refer to the ‘Operating instructions’ [1]. As the standard option the flow computer can work with up to 5 internal pre-defined PVT data sets for a corresponding number of wells. Changing between data sets can easily be controlled from the operator’s control system by remotely sending the desired well number to the Roxar MPFM 2600 flow computer. This can also be controlled from the service console PC. In addition to the 5 internal PVT data sets, a theoretical infinite number of PVT data sets can be selected and downloaded from set-up files stored in the service console PC.



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9. WETGAS MODE The Roxar MPFM 2600 may be supplied with Wetgas algorithms as an option. These algorithms are utilizing the same hardware as the standard Roxar MPFM 2600. There is no need to add any components to the meter. However to achieve the optimal accuracy for the extreme GVF conditions seen in classical Wetgas applications it is recommended to perform additional calibration at the factory. This would be a static calibration to optimize the field electronics. It is therefore an advantage if the Roxar MPFM 2600 is initially purchased with Wetgas software if the unit is intended to use at such applications. The Roxar MPFM 2600 requires a representative hydro carbon fluid analysis report as input to the algorithms. Based on this the Roxar proprietary software PVTx generates a VLR-PVT table in addition to the density and black-oil-table. See Figure 28 for a view of the VLR table.

Figure 28



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(LIVE measurement) (LIVE measurement) (LIVE measurement) (LIVE measurement)

DP Impedance P & T PVT

Hydro Carbon Properties @ MPFM 2600

Phase Fractions

Flow rate calculation

Qcond

Qwater

Qgaas

Total Hydro Carbon Mass

Water Volume Fraction

Kindly see the flow chart (Figure 29) for a functional overview of the Roxar MPFM 2600 wetgas mode, with the measured variables and the input values. As seen in the flow chart, the VLR (Hydrocarbon vapour liquid ratio) is calculated from the PVT in combination with the P&T measurements. The impedance field electronics provide the WVF (Water volume fraction). Roxar applies these measured variables and input values with extrapolated standard MPFM equations specially adapted for Wetgas operation. There are requirements for start up and commissioning of a Roxar MPFM 2600 Wetgas:

- Hydrocarbon composition has to be available to generate a VLR table in PVTx (PVTx 6.6 and up).

- A selection of wells has to be tested with a WLR sample available to verify the impedance calibration.

Figure 29



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10. SYSTEM PERFORMANCE AND CHARACTERISTICS

10.1 Standard specification The specifications below are for a cost optimum solution that will meet most operator requirements. System performance and characteristics Operating range: • 0-100% water in liquid ratio (WLR) • 0-100% gas volume fraction (GVF) Meter sizes: •4”50mm, 4”67mm, 6”87mm, 8”132mm, 10”173mm Installation: • Vertical upwards flow Typical uncertainty (95% confidence int.): • Liquid rate: +/-3.5% relative • Water cut: +/-2.5% absolute • Gas rate: +/-6% relative Design pressure: • 5000 psi (345 bars) Operating temperature: • Up to 130 °C (266 °F) Mechanical and electrical components Meter body Wetted parts materials: • Duplex UNS 31803 (Electrodes: Inconel) Flange connection: • Grayloc/Techloc® hub flanges Length: • 650 mm (4”) Weight: • 110 kg (4”) Venturi • Insert design, field replaceable • Compact isolation valve and manifold • Rosemount 3095 Multivariable™

Transmitter (DP, P & T)

Density measurements Roxar non-Gamma software: • Suitable for GVF<85% Roxar compact Gamma system: • Recommended for all applications • Source: Cs-137, 1-5 mCi, Half-life 30.1

years • Detector: Roxar T205 Sensor technology DP 26 – Multi electrode, dual plane Roxar ZectorTM technology Power supply Voltage: • 18-36 VDC, 100-240 VAC Power consumption: • 12W Communication interface Com ports: • RS-232/RS-485/Ethernet Communication protocol: • Modbus ASCII/RTU/TCP Electrical certification • Sensor electronics: Ex-i • Compact Gamma detector: Ex-d • Flow computer: Ex-d or safe area Software • Roxar Fieldwatch • Roxar Service Console Add-on modules: • Acoustic Sand monitor •Well test package, PVTx, Communications, +++



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10.2 Operating range Typical operating envelope for a 4”67mm meter shown below in Figure 30

Figure 30

Typical operating envelope for a 6”87mm meter shown below in Figure 31

Figure 31



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10.3 Measurement uncertainty

10.3.1 Measurement uncertainty for the Roxar MPFM 2600 Multiphase mode:

Performance specifications:

Roxar MPFM 2600 Multiphase mode

Input requirement: Hydrocarbon Fluid Composition with plus fraction

properties and water density as input (if water production)

Confidence level: 95% (k=1.96) Combined expanded meter uncertainties

Sub range GVF range Gas Liquid WLR

A 0 – 25 % 8(1) 3 2,0

B 25 – 85%

6

3,5 2,5

C 85 – 95 % 5 3,5

D 95 – 98 % 8,0 (2) 4,0(2)

E 98– 100% _(2) _ (2)

Repeatability: ¼ of % ¼ of % ¼ of %

The uncertainties above are valid for line pressure > 10 barg.

For line pressure < 10 barg, the above uncertainty spec must be multiplied by a factor of 1.3.

MULTIPHASE MODE: Sub range A, B, C and D (the meter will function in sub range E in Multiphase mode but with non-quantified uncertainties for liquids and WLR)

NON-GAMMA MODE: The Roxar MPFM 2600 can optionally be supplied in a non-Gamma version. In such a case, the above uncertainty table must be multiplied by 1.2 for sub range A & B.

Non-gamma mode in sub range A is only for single well applications.

Non-gamma mode in sub range B is for multiple wells, and single well applications. (1) For GVF > 5%. (2) The Roxar MPFM 2600 can optionally be supplied with a Wetgas software module, specially designed for ultra high GVF applications (95 -100 % GVF). Please refer to the separate uncertainty specification for the Wetgas mode.



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10.3.2 Measurement uncertainty for the Roxar MPFM 2600 Wetgas mode:

Performance specifications:

Roxar MPFM 2600 Wetgas mode

Input requirement: Hydrocarbon Fluid Composition with plus fraction

properties and water density as input (if water production)

Confidence level: 95% (k=1.96) Combined expanded meter uncertainties

Sub range GVF range Total HC (%rel) WVF (%abs) Sensitivity %

A,B,C 0 – 95 % _(3) _(3) _(3)

D 95 – 99 % 5 0.2 0.005

E 99– 100% 5 0.2 0.005

Repeatability: ¼ of % ¼ of % ¼ of %

WETGAS MODE: Sub range D,E.

The selection between Multiphase- or Wetgas-mode may be automatically or manually (operator) selected if both modes are installed.

(3)Multiphase mode is used.

Wetgas Mode input requirement and operating pressure:

Hydrocarbon Fluid Composition and water density as input (if water production)

The uncertainties in Wetgas mode are only valid for line pressure > 15 bar (g) in the full specified GVF range. For line pressure less than 15 bar (g) please contact Roxar for a discussion.



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Influence quantities

Salinity:

Variations in water salinity have no effect whatsoever on watercut readings under all process conditions with less than 60-80% watercut.

Sand:

Sand has dielectric properties very close to those of oil. Hence, any sand will be measured as a part of the oil. However, as the dielectric measurements are volume based, sand will have extremely little effect on the performance of the meter. Roxar has no experience with any sand effects on any installation as per today.

Flow regime:

Studies have shown that phase slip varies greatly with changes in process conditions and flow regime. Whereas the Roxar system physically measures this phase slip, other systems require complex ‘Slip Models’ that can only provide an estimation of the slip based on estimates of the flow regime.

Methanol injection:

The meters water cut measurement will be influenced by significant methanol injections. The methanol will be interpreted as water, but if the amount of methanol injection is known it can be compensated for.

Additives, e.g. emulsifiers, wax inhibitors, corrosion inhibitors

Roxar has never experienced any effects of inhibitors on any installation.

H2S:

The meters performance is not influenced by H2S. Materials selected for application where H2S content is high (E.g. Inconel 625 sensor body).

Scaling:

The Roxar Multiphase meter 2600 can accept a minimum amount of scale without effects on the measurements. However Roxar advice to remove thick conductive layers of scale from the meter internals. The internals of the meter are not prone to builds up of scale layers due to the PEEK material which keeps the electrodes in flush with the flow.

Wax:

Wax present in the flow or deposited inside the sensor will be measured as oil. This is due to the fact that the density and dielectric properties of wax and oil are very close. Extreme wax deposited inside the sensor may limit the flow area and lead to too high flow rate readings. However, typically wax inhibitors used to prevent wax deposition do not affect the measurements performed by the meter. Lastly, since the Roxar Multiphase 2600 is full-bore and non-intrusive, thick layers of wax are unlikely to build up inside the meter.

Hydrates:

The Roxar MPFM 2600 does not have any instrument tubing, and has a compact isolation valve flanged to the meter body, this reduces the possibilities for hydrates. The delta pressure tapping is ring-room design that again will provide better pressure tapping and again assist in reducing the risk of hydrates. Moreover, in applications found to be in high risk as of hydrate formation, self regulating heat tracing provides an extra insurance towards hydrate formation.



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Fluid properties:

The Roxar Multiphase meter 2600 has a configuration which contains information about the fluid properties like oil/water/gas densities and oil permittivity. These properties will change over time as a function of pressure and temperature changes, but the Meter will automatically calculate new densities with the coherent process conditions based on given PVT – tables generated from PVTSim software. However if there are significant hydrocarbon fluid composition changes and water density as production decline, these changes should be identified to count for these changes. This is done by generate new PVT – tables based on new input, and if not this could result in erroneous measurements. However, the Roxar Multiphase meter 2600 can tolerate relatively large changes in fluid properties before the error becomes significant. For example: a change in oil density of +1% relative will result in an error of only +0.9% in measured liquid flow rate. See also table below:

Quantity Change % rel

Liq. rate % rel

WLR % abs

Gas rate. % rel

Note

Oil density +1 % +0.9 % -0.2 % -0.2 % 1

Gas density +10 % +1.1 % -0.3 % -0.3 % 1

Water density +1 % +0.3 % -0.1 % -0.1 % 1

Oil permittivity + 5 % -0.3 % +1.3 % +0.1 % 1

Water conduct + 1 % -0.2 % + 0.9 % - 0.0 % 2

Notes: 1: Given at 80% GVF, 20 % WLR 2: Given at 80% GVF, 80 % WLR

Rated conditions of use:

Pressure: < 345 bar Temperature: -20 - 130oC

Oil density: 600 - 1050 kg/m3 Oil viscosity: No influence

Water density: 950 - 1200 kg/m3 Gas viscosity: No influence

Flow regimes: All regimes (single phase, bubbly flow, churn flow, slug flow, annular flow)

References (documentation)

1. NFOGM Handbook of Multiphase Flow Metering, Rev 2. [2]



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Calculation of oil and water flow rate uncertainty: ( )( )

WLRUUWLR

U WLRliqOil -

+×-=

1

1 22

( )WLR

UUWLRU WLRliq

Wat

22 +×=

Where Uoil : Relative uncertainty of oil flow rate Uwat : Relative uncertainty of water flow rate Uliq : Relative uncertainty of liquid flow rate WLR : Water in liquid ratio (‘water cut’) UWLR : Absolute uncertainty of water cut

Repeatability: ¼ of measurement uncertainty Uncertainties: Based on 95% confidence interval as described in the NFOGM handbook of Multiphase Metering [2]

4.1 functional design specification (fds)

Documents

ray attenuation

volumetric

meter specific

pc104 flow

advanced signal

zectortm technology

service console

impedance