crude&hydrocarbon measurement

8/6/2019 Crude&Hydrocarbon Measurement

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Crude And Hydrocarbon Measurement Technologies

Youssef Farid BasrawiSpecialistFlow MeasurementsSaudi Arabian Oil Company (Saudi Aramco)Dhahran, Saudi Arabia 31311

KEYWORDS

Applications of Crude and Hydrocarbon Flow Measurement Technologies, Better Accuracy and Finer

Precision Yield Proper Accountability and Tremendous Savings.

ABSTRACT

The paper talks about the principles and applications of current and emerging crude and hydrocarbonflow measurement technologies. It highlights the applications of flow metering technologies, in theworld and in the Kingdom of Saudi Arabia. Emphasis is put on better precision and higher accuracy in

volumetric and mass custody and royalty transfer through put measurement, of crude and hydrocarbonfluids. Through finer precision and higher accuracy, when applied to exports and domestic consumption,proper accountability can be achieved and tremendous cost savings realized. We cannot be held

accountable for what we can not measure . Topics of presentation consist of the science ofmeasurement, application of current and emerging technologies in the world of hydrocarbonmeasurements and the proactive role Saudi Aramco is playing in this research and application. The

technologies that will be briefly discussed are, the use of the master meter in certifying crude andproduct meter provers as an applied technology and its comparison in accuracy to conventional methodsof meter prover certification. Other devices consist of the principles and sciences of gas flow

measurement, the various water- in- crude detection instruments, currently under research in SaudiAramco and the application and viability to custody measurement, where accuracy is far more stringent

than that of process condition, of the new mass and hellicoidal flow meters.

A brief outline of the presentation is as follows: Measurement - The philosophy & science.


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The role of Saudi Aramco in the national and international arena of measurements in the crude andhydrocarbon industry.

Need for better accuracy and finer precision for proper accountability. The principles and application of the various types of flow measuring devices and instrumentation. Recommendations.

INTRODUCTION

For custody and royalty transfers of exports and domestic consumption, accuracy and fine precision play

the key role in influencing the current applications of crude and hydrocarbon products flow measurementtechnologies. Saudi Aramco is playing a proactive role in such applications, domestically andinternationally. Such technologies are; the application of the master meter technology in certifying crude

and product meter provers, its cost effectiveness, operational benefits and accuracy. Other devices

consist of the principles and sciences of gas flow measurement, the various water- in- crude detectioninstruments, currently under research in Saudi Aramco and the application and viability to custody

measurement, where accuracy is far more stringent than that of process condition, of the new massandhellicoidal flow meters.

MEASUREMENTS

The Science and Philosophy. A reference standard used for the quantitative comparison ofproperties. The quantitative and numerical assessment of the dynamic and static properties ofnaturally occurring phenomena and substances. In the hydrocarbon industry this is translated to the

measurement of fluid flow and static tank gauging. Examples of fluid properties:

- Cold (absence of heat) Temperature (T) (F-C).

- Mass Volume (V) Cubic Length (cu. ft.- cu. m.).- Energy Velocity (S) Length/Time (ft./s. m./s.).- Rate Flow (Q=V/t) Cubic Length/Time (cu. ft./s.-cu m./s.).

Other parameters are pressure, viscosity, density and so on.

TYPES OF MEASUREMENTS

Royalty Transfer. A specialized form of measurements. The basis for paying a fee or percentage ofthe revenues generated by the sales (royalty) to owners of private or state owned enterprises.


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Custody Transfer. A measurement of transfer of a deliverable at the point of change ofresponsibility, providing quantity and quality information used for the physical and fiscaldocumentation of a change in ownership and/or responsibility of commodities between two partiespossessing a contractual agreement and bound by the terms and conditions of such a contract.

APPLICATIONS TO CUSTODY TRANSFER OF CRUDE & HYDROCARBON

LIQUIDS

Global Overview. Necessity dictates inventions. If we are to account quantitatively for what weperceive as naturally occurring phenomena, we need to devise accurate and precise measurementmethods to obtain meaningful information and use it to ensure credibility and integrity of oursystems. Measurement is an institution:

- International Standard Organization (I.S.O.), France.- National Institute for Standards and Testing (N.I.S.T.), U.S.A.

- American Petroleum Institute (A.P.I.), U.S.A.- Institute of Petroleum (I.P.), Europe.- Instrument Society of America (I.S.A.), U.S.A.

- Saudi Arabian Standards Organization (S.A.S.O.), K.S.A.

Hydrocarbon Industry. Measurement of hydrocarbon fluids was conceived by economicaldemands, so the need for economical resources of fuel and energy becomes imperative. Hydrocarbonfluids, to date, are the most economical source of fuel and energy.

Loss Control And Risk Management. In recent years, the prices of fuel and crude dictated thataccuracy and precision be enforced, especially when large volume throughputs of crude and

hydrocarbon products exchange custody between supplier and consumer. Laboratory Analysis. Laboratory analysis in the hydrocarbon industry comprises of Sediment

analysis and API Gravity & Composition determination.

Saudi Aramco. As part of the Saudi Aramcos ongoing objectives to continuously maintain worldclass operational standards, measurement of crude and gas output volumes must be conducted with

the utmost accuracy. This is accomplished by effective monitoring, enforcement and compliance

with government as well as international measurement standards and requirements, ensuring properdesign, installation, and operation of royalty and custody metering facilities. These objectives areapplied in refineries, terminals, gas plants, pipelines and tank farm operations. They are also applied

to crude and hydrocarbon royalty/custody transfer measurements, loss control and surveys ofmeasurement facilities. Figure1 shows the sales and distribution facilities of the hydrocarbon

industry.


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North

Scale: 1cm: 3000km Legend: Sea LandFIG. 1 - WORLD SALES AND DISTRIBUTION FACILITIES

ACCURACY, PRECISION AND PROPER ACCOUNTABILITY

Measurement Accuracy. Achieving consistent high accuracy measurements is the primary purpose.Custody Transfer Measurement Facilities can achieve an accuracy of better than + 0.25%. Figure 2show the measurement accuracy profile. Shown in Table 1 are potential annual revenue losses due

to lack of proper accuracy, precision and accountability.

FIG. 2 - MEASUREMENT ACCURACY PPROFILE


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TABLE 1- POTENTIAL ANNUAL LOSSES FOR CRUDE AND HYDROCARBON

PRODUCTS.

Crude Oil = 8 MMBPD 0.5 % Error = 40 MBPD @$ 15.00 / BBL = $ 600,000.00/ D

PETROLEUM LOSS Liquefied Petroleum GasLPG = 600 MMBPD

0.5 % Error = 3 MBPD@$ 12.00 / BBL = $ 36,000.00 / D

Natural GasNG = 2,700 MSCFD.

0.5 % Error = 13.5 MMSCFD@ $ 0.50/ MSCF = $ 6,750.00 / D

HYDROCARBON PRODUCT LOSS GasolineDiesel = 600 MBPDJet Fuel

0.5% Error = 3 MBPD @$ 22.00 / BBL= $ 66,000.00/D

TOTAL POTENTIAL ANNUAL LOSS + 0.5% Measurement Error $ 255,150,000.00 which is nonrecoverable .

Measurement Precision.The primary purpose for better precision is to achieve and maintain properaccountability, insurance of flow measurement systems integrity and above all satisfaction betweencustomer or client and supplier.

Proper Accountability. We cannot be held accountable for what we cannot measure. Properaccountability can be achieved by the application of:- Proper control: effective monitoring and utilization of measurement procedures, traceable to

primary standards, to ensure accurate design and correct installation of measurement facilities.- The optimization of measurement systems: minimizing loss and providing more efficient

operation and measurement facilities.

- Application of cost effective measurement equipment and technologies.

TYPES OF FLOW MEASUREMENT DEVICES

There are fundamentally two types of flow measuring devices:

Direct Measurement Devices.Direct measuring devices are devices that use the fluid properties asdirect measuring parameters to determine the fluid flow rate. Such parameters are mass, density,

viscosity temperature, pressure etc. Examples are: Positive Displacement Meters and Mass Flow

Meters. Inferential Measurement Devices. Inferential measuring devices use parameters other than the

fluid properties, such as electronic pulse counts, meter factors, system factors, linear and rotationalvelocities components of measuring devices to infer the fluid flow rate. Examples are: Turbine,

Hellicoidal, Orifice Plate, Vortex, Venturi and Ultra Sonic Flow Meters. Other measurement devicesassociated with fluid flow are: Temperature, Static and Differential Pressure Measuring Devices(Transmitters, Chart Recorders, Manometers, DP Cells), Densitometers, Viscometers and so on.


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PRINCIPALES AND APPLCATION OF MEASUREMENT TECHNOLOGIES

Crude and hydrocarbon product measurements consist of two types. Volumetric and Mass Flow.Accuracy and precision play the key role in influencing the current applications of volumetric and massmeasurement technologies when applied to royalty and custody transfers for exports and domestic

consumption. Amongst the technologies being applied are, the use of the master meter in certifyingcrude and product meter provers as an alternate to conventional prover certification method usingwaterdraw; the principles and sciences of the various water- in- crude detection instruments currently

under evaluation in Saudi Aramco and the new mass and hellicoidal flow meters and their application inwell heads and viability in custody measurement applications where accuracy requirements are far more

stringent than those of process applications.

Volumetric Flow.Master Meter for Meter Prover Certification.The standard method of calibrating any pipe prover

involves a determination of the volume, displaced between detectors at standard conditions (15 DegC/ 60 Deg F, and 101.325 kPa/14.73 Psia). The details are given in the A.P.I. (Manual for Petroleum

Measurement Standards Chapter 4 " Proving Systems " 1997). Displacer is made to move from thelaunch chamber toward the detector switch by the action of the 4-way valve. The measured volume isthe volume displaced by the displacer, starting from the instant the displacer activates the first

detector to the instant it contacts the second detector on the other side of the prover. This is calledone pass. The 4-way valve is reversed and the same procedure is repeated in the opposite directionfor the second pass. The sum of the two passes or round trip is the measured volume of the prover.

Figure 3 shows a graphic representation of a Bi-Directional U-Shaped Pipe Meter Prover.

FIG. 3 - BI-DIRECTIONAL U-TYPE PIPE METER PROVER

Fluid is introduced into the master meter, master prover (or master certified test measure) and the

prover to be calibrated. Trial runs of the master meter are made against the master prover or mastertest measure to calculate its meter factor. This is achieved by comparing pulse counts generated by

the pulse generator of the meter against the known volume of the certified test measure, for severaltrial runs. The prover volume is then determined in the same fashion.


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The pulse generator starts pulse count as soon as the displacer gates the detector and continues tocount pulses until the second detector is gated and the pulse counts stop. This is considered a pass or

half trip. The sum of the pulse counts of the two passes or round trip is translated into volume andcorrected for standard conditions. Figure 4 shows a graphic representation of a prover certificationusing the master meter method and Figure 5 shows a graphic representation of a Master Meter Skid.

FIG. 4 - MASTER METER PROVER CERTIFICATION FIG. 5 - MASTER METERWater cut Meter.The dielectric constant and conductivity of water are much higher than that foroil. This difference can be utilizes to measure the water content of oil/water mixtures. The water cutmeters measures the microwave dielectric properties of mixtures using the resonant cavity method.

The density of a material in the tube affects the natural vibration frequency of a tube. By measuringthe frequency, one can measure the density of the material. A resonant cavity is a metal structure,which confines an electric field and causes it to reflect back and forth within the cavity. If the

wavelength of the electromagnetic waves equal one of the dimensions of the cavity, then the multiplereflecting waves constructively interfere and generate a standing wave: electric field resonance. Ifone fills a resonant cavity with a material, the resonant frequency of the cavity will shift by an

amount directly related to the dielectric constant of the material. The width of the resonant peak is

related to the conductivity of the material in the cavity. Thus by measuring the resonant frequencyand peak width, one measures the dielectric properties of a material in the cavity. Figure 6 shows agraphic representation of a Water cut Meter.

FIG. 6 - WATER CUT METER


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Helicoidally Flow Meter. The hellicoidal flow meter operates in a very similar fashion to theturbine flow meter, except that the conventional turbine meter requires straightening vanes upstreamto laminate the fluid flow. The main difference is that the blades of the helliciodal meter are as the

name implies. The Fluid flowing through the hellical blades causes rotation at a speed directlyproportional to the flow (within certain limitation of flow and viscosity); each revolution thus

corresponding to a precise and constant volume throughput. A magnet (one or two) mounted in therotor induces electrical impulses in an adjacent pickup coil. These are then processed by an electricalconverter and displayed as a flow rate. Figure 7 shows a graphic representation of a Hellicoidal FlowMeter.

FIG. 7 - HELLICOIDAL FLOW METER

Sonic Flow Meter. The use of highly sophisticated techniques enables us to detect very small timedifferences. These small time differences make it possible to reach a measuring resolution as low as1mm/s. the ultra sonic flow meter takes advantage of the principle that an ultrasonic pulse travels

faster downstream while slower upstream. The larger the difference in time between the two pulsesthe more fluid passes by. Because ultrasonic meters do not rely on kinetic energy from the fluid, verylow flow rates can be detected. This results in a very high turn down (typically 50:1) and no pressure

drop.Figure 8 shows a graphic representation of a Sonic Flow Meter.

FIG. 8 - SONIC FLOW METER

Orifice Plate Flow Meter. The most widely used head device in the gas industry is an orifice meter.

The primary element is installed in the pipeline carrying the fluid and consists of a meter run, ortube, and an orifice plate inside an orifice fitting. The orifice that is bored through the plate createsthe restriction. The fitting has pressure taps drilled into the flanges on either side of the orifice plate.


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The upstream tap senses static, or flowing pressure usually expressed in psia or psig. Thedownstream tap senses the pressure of the flowing fluid after it passes through the orifice. Under

normal conditions, downstream pressure at the tap is lower than upstream pressure. Since thepressure on one side of the orifice is different from pressure on the other side, a difference inpressure exists. This pressure difference is termed differential pressure usually expressed in inches

of water. Differential pressure is expressed in inches of water when a U-tube, or manometer, withwater in it is used. Water in a U-tube moves if pressure is applied to either end of the U. If a scale, orruler, marked in inches is placed alongside the U-tube, the number of inches of water movement

caused by pressure can be noted. Very small amounts of pressure cause a relatively large amount ofwater movement within the tube. In some cases, however, a water manometer cannot be usedbecause the pressure of the flowing fluid in the line exceeds a manometers pressure rating. Gauge

lines, which are usually small-diameter lengths of stainless steel tubing, come out of the pressuretaps and transmit upstream and downstream pressure to the secondary element. The secondaryelement contains pressure-sensing devices and a flow recorder or other type of recording instrument

to record static and differential pressure. The pressure-sensing device may be a bellows meter or apressure transducer that puts out an electrical signal. A bellows meter is shaped like a very small

accordion. Pressure causes the bellows to move back and forth, and the movement is linked to therecorder. A pressure transducer senses pressure changes and transmits them electrically to computersor other electronic devices. The dynamic flow equation for the orifice plate is derived from the basic

mass and energy conservation laws and Newtons laws of motion. This equation can be expressed as

Qv = Cv(hwp)1/2 where Qv is the volumetric flow through put in cubic inches or feet per second or

minute, Cv orifice discharge coefficient, hw static pressure in inches of water column and p is thedynamic pressure difference in psia or psig which creates the flow through the orifice bore. Figure 9

shows an orifice meter installation.

FIG. 9 - ORIFICE METER INSTALLATION

Mass Flow.Coriolis Mass Flow Meter. Assume you are standing in the center of a merry-go-round rotating with anangular velocity w (for clarity one revolution per minute). You start to walk at a constant speed from thecenter to the edge of the merry-go-round. When passing A you are covering the distance A and when

passing B you are covering the distance B both in the same one minute. It is clear that the distance B ismuch greater than the distance A. Apparently you have been accelerating . You have a certain mass and


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from Newtons second law Force = mass x acceleration. So there must be a force. This force andacceleration is named after Coriolis and are the basis for the mass flow meters. The Coriolis force Fc

prevents you from arriving at the point you were originally heading for. The resulting deflection D is ameasure of the Coriolis force and as such the mass. The faster you walk the larger the deflection. Thistype of meter measures the mass of the fluid flowing through vibrating U or S shaped tubes. As the

fluid flow through the vibrating tubes, the naturally occurring Coriolis force causes a slight rotation ofthe meter tube about its axis, which is proportional to the amount of mass flowing in the tube. Thesemeters can also measure density as function of the tubes natural frequency. Figure 10 shows a graphic

representation of the principle of the Coriolis Force. Figure 11 shows a graphic representation of theCoriolis Mass Flow Meter. Table 2 shows some attributes of the flow measurement devices mentionedthroughout this paper.

FIG. 10 - CORIOLIS FORCE Fc FIG. 11 - CORIOLIS FORCE MASS FLOWMETER

TABLE 2 - ATTRIBUTES OF FLOW MEASUREMENT DEVICES.

TECHNOLOGY ACCURACY COST SAVINGS ADVANTAGES DISADVANTAGESMASTERMETER

Comparable ToWaterdraw Volume,0.05% Deviation.0.02% Repeatability.

$25,000 $500,000.00 &15,000.00 ManHours Annually.

Accurate.Repeatable.Calibration withProcess Fluid.

Traceable to SecondaryStandards.

WATER CUTMETER

0.05% For 0 to 1%Water In Crude.0.5% For 1 to 20%Water In Crude. 1.0% For 20 to 50%

Water In Crude. 5.0% For 50 to100% Water In Crude.

$50,000 Labor, Operation,& MaintenanceCost.

In Line Reading.Minimum PressureDrop.TemperatureCompensated.

Easy Calibration.

Requires MixerUpstream.

HELLICOIDMETER

0.25% Of Reading.0.02% Repeatability


Single RotatingElement.Low Press. Drop.Linearity Unaffectedby Viscosity.

Poor Performance On DryWaxy Crude.


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SONIC METER 0.25% Of Reading.0.02% Repeatability.Can Detect Flows AsLow As 1mm/s.

$ 5,000 Labor, Operation,& MaintenanceCost.

Bi Directional FlowCapacity.Repeatable.No Press. Drop.No Moving Parts.

Works Well Only On DryFluids.

ORIFICE METER 0.5-1.0% Of

Reading. 0.02%Repeatability.

$3,500 Labor, Operation,

& MaintenanceCost.

No Moving Parts.

Flow Expressed InVolume or Mass.

Requires Flow

Conditioner Upstream.Secondary StandardTraceable.

MASS METER 0.2% Of RateOperated At FluidVelocities Between0.12 & 12. m/s(0.4 and 40 f/s).


Direct Mass Measure.No Moving Parts.Unaffected byTemperature.

High PressureDrop for LowFlow Rates.

CONCLUSION

In conclusion to this paper Crude and Hydrocarbon Measurement Technologies the main point arebriefly summarized and recommendations are offered.

Summary of Main Points.- Measurement: The Philosophy and Science.

A reference standard used for the quantitative comparison of properties. The quantitative andnumerical assessment of the dynamic and static properties of naturally occurring phenomena and

substances.- The role of Saudi Aramco in the national and international arena of crude and hydrocarbon

measurements. Effective monitoring, enforcement and compliance with government

guidelines (Ministry of Petroleum and Mineral Resources) as well as international measurementstandards and requirements to ensure proper design, installation, and operation of royalty andcustody metering facilities.

- Need for better accuracy and finer precision for proper accountability.

We cannot be held accountable for what we can not measure. Through finer precision andhigher accuracy, proper accountability can be achieved and tremendous cost savings realized.

- Types of Flow Measuring Devices.

Direct and Inferential Measurement Devices.- Principles and application of measurement technologies.

Volumetric and Mass Flow Meters.

Recommendations.- Better accuracy and finer precision through application of new and more cost effective

measurement technologies.- Continued participation and proactive representation in national and international measurement

engineering and loss control institutions.- Effective monitoring and application of measurement and loss control standards to measurement

facilities for compliance and quality assurance.- Monitoring and continued development of measurement training programs.


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ACKNOWLEDGEMENTS

Ministry of Petroleum and Mineral Resources. Custody Measurement Unit, Consulting Services Department, Saudi Aramco. Petroleum Loss Control Unit, Terminal Operations Department, Saudi Aramco. Juaymah Gas Plant Engineering Division ,Juaymah Gas Plants Department, Saudi Aramco. Ras Tanura Refinery Operations Department, Saudi Aramco.

REFERENCES

American Petroleum Institute 1993; Manual of Petroleum Measurement Standards, Washington; API Miller R.W. 1996; Flow Measurement Engineering, New York; McGraw-Hill. Spink L.K. 1972; Flow Measurement Engineering, Massachusetts; The Foxboro Company.

crude&hydrocarbon measurement

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