ALASTAIR MCLACHLAN Applications Cameron

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3 ALASTAIR MCLACHLAN Applications Cameron Have worked in the oil and gas flow measurement industry for 27 years primarily in custody transfer measurement using ultrasonic meters. Joined Cameron Caldon Ultrasonics in 2007 as the Applications Manager responsible for application engineering and customer support for Europe, Middle East and Africa. Previous experience in Flow Computers and control systems. B.Sc. In Electrical and Electronic Engineer and a Chartered Engineer

4 Principle of operation High viscosities and low Reynolds numbers Calibration Proving Custody Transfer Ultrasonic Meters Improving Repeatability Test data Summary and Conclusions

5 Principle of Operation

6 Transit Time Principle Transit time meters operate on the principle that the speed of transit of an ultrasonic signal depends on the speed of the fluid through which it travels In practice industrial ultrasonic meters use short pulses of ultrasound, with each transducer being used alternately as transmitter and receiver

7 Transit Time Transit times with no flow t up t down

8 Transit Time Transit times with flow t up t down

9 Transit Time Theory D L

10 Transit Time Measurement Theory

11 Viscosity and Reynolds Number Considerations

12 Reynolds number considerations Why are we concerned about Reynolds number? Used in fluid mechanics to describe the balance between the forces of momentum (flowrate) and friction (viscosity) Reynolds Velocity diameter no kinematic viscosity The characteristics of the flow depend on Reynolds number

13 Laminar flow Reynolds number < 2,000

14 Turbulent flow Reynolds number > 10,000

15 For custody transfer performance with standard meters, Cameron will normally impose a minimum Reynolds number limit of 10,000 What does this mean in terms of viscosity? Re UD Assume a 1 m/s lower velocity limit and

16 Viscosity corresponding to low Re Re < 1 m/s Re < 1 m/s Re > 1 m/s

17 Somewhere below 10,000 Reynolds number the flow becomes transitional, continually switching back and forth between turbulent and laminar flow profiles:

18 What does this transition do to ultrasonic meter performance?

19 Error (%) Full bore meter performance 1.0% 0.8% 0.6% 220 cst, 20 deg C 115 cst, 30 deg C 55 cst, 45 deg C 0.4% 0.2% 0.0% -0.2% 2-path 2-path 3-path 4-path 5-path (Caldon 220CA ) (Caldon 240C) -0.4% -0.6% -0.8% -1.0% 100 1,000 10, ,000 Pipe Reynolds Number

20 Reducing elliptical nozzle shaped inlet Substantial diameter/area reduction Beta < 0.64, area ratio < 0.41 Downstream pressure recovery cone

21 Velocity profile is flattened and forced into a more steady condition by the reducing nozzle Reducing Nozzle Recovery Cone

22 Normalised Path Velocity Normalised Path Velocity Modified flow profile behaviour No reducing nozzle With reducing nozzle Re = 1,000 Re = 7, Re = 1,000 Re = 7, Path Radial Location Path Radial Location

23 Modified profile behaviour smoothing out the laminar/turbulent transition

24 Equals PD meter performance even through the laminar/turbulent transition region OIML certified with no Reynolds no. limitation

25 Secondary Benefit: Shorter Paths and Higher Velocity Help Combat High Absorption in Viscous Oils

26 Amplitude vs distance and viscosity

27 Relative to a full bore meter the path length is reduced and the velocity is increased

28 Calibration

29 Performance Accuracy: Linearity, repeatability, reproducibility Reliability Traceability Every barrel the same Defined as property of a result of a measurement whereby it can be related through an unbroken chain of comparisons all having stated uncertainties

30 Calibration Options Ultrasonic meters can be provided with traceability by calibration in-situ or in a laboratory ( central proving ) The choice of a method that is fit for purpose is based on an assessment of the uncertainty and consideration of the economic, logistical and regulatory issues

31 Complexity & Cost vs Uncertainty $ Cost of metering system Financial exposure Permanent prover Laboratory calibration Increasing uncertainty

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33 Complexity & Cost vs Uncertainty Although a system with an installed prover is more complex and more expensive, it does offer the opportunity for the lowest installed uncertainty, and the ability verify the meter on a relatively short timescale This means that in-situ proving is generally preferred for most custody transfer applications, as recognised in API 5.8

34 Calibration Process For Caldon meters the calibration process typically involves tests on multiple fluid viscosities and entry of the resulting data in a look up table in the meter s electronics This creates a meter that is insensitive to changes in viscosity/reynolds number over the range covered by the test fluids

35 Raw Calibration vs Flow Rate

36 Raw Calibration vs Reynolds Number

37 Calibration The data is arranged in the form of two curves of meter factor versus Reynolds number and profile flatness This data is then entered into the flow meter electronics, where the Reynolds number and velocity profile shape are calculated without the need of user inputs The result is a meter that is linear even when the fluid viscosity changes over a wide range

38 Final Calibration

39 Method acknowledged in NMi certification If a measurement sensor is intended to be used with single or multiple liquids without adjustments, then the sensor has to be calibrated over the applicable range of Reynolds number, using one or more fluids, while the accuracy conditions are met for each fluid.

40 Proving liquid custody transfer ultrasonic flowmeters

41 Proving Background Industry expectations are based on turbine meter experience Turbine meters are generally very repeatable Naturally, when a new technology comes along it is compared with the old

42 USM experiences have been clouded by a variety of issues including poor results owing to low sample rates, or calculation and output delays These issues can be overcome by careful design in terms of sample and output update rates, however...

43 Even once a very fast sampling, calculation and update rate is used, the repeatability of a full-bore multipath ultrasonic meter may not compare favourably with a turbine meter, and the industry norm of 0.05 % spread in 5 runs can be difficult to achieve The fundamental issue to be overcome is the effect of turbulence

44 Flow with turbulence

45 Averaging the random turbulence Average velocity with superimposed turbulence Average velocity Ultrasonic velocity sample

46 Averaging the random turbulence Average velocity with superimposed turbulence Average velocity Ultrasonic velocity sample

47 Averaging the random turbulence Average velocity with superimposed turbulence Average velocity Ultrasonic velocity sample

48 Averaging the random turbulence Average velocity with superimposed turbulence Average velocity Ultrasonic velocity sample

49 Turbulence So... The effects of turbulence are random and can be reduced by averaging However, it is not the sample rate of the meter that is the limiting factor, it is the frequency of the turbulence As the turbulent features in the flow travel at the flow velocity, the number that pass through the meter is proportional to volume passed

50 This highlights an important practical issue, that any statement of repeatability for an ultrasonic meter can only be usefully interpreted if accompanied with information on the volume used

51 Reference standard deviation Performance of any flow meter can be characterised by measuring the standard deviation of the calibration results and normalising it to a reference volume S ref is the standard deviation normalised to a volume of 1 m 3 s ref s V

52 Uncertainty U t n s t 95, n 1 95, n 1 s nv ref Prove run volume V 95, n 1 s ref is the only input that is dependent on the meter and flow characteristics 1 n t U s ref 2

53 These are essentially the same calculations used to produce table B-2 in API Chapter 5.8 (2005)

54 The API table B-2 recommended volumes were dropped from the 2011 revision Various views - smaller/larger than needed, or too large to be practical They do not fit every meter in every situation Some manufacturers advocate a prover/turbine master meter combination to achieve larger volumes; there is nothing wrong with this, but it is not necessary for all models of ultrasonic meter

55 Cameron have developed tools to allow the calculation of prover volumes for Caldon meters Inputs required are the meter size and model, the number of runs to be used for proving and the desired success rate Success rate relates to the statistical assessment of acceptance of proving data, i.e. a success rate of 66 % would mean that proving repeatability would be acceptable on average two out of three times

56 The required prover volume decreases if the number of runs selected is increased Likewise, for a given prover volume, the success rate will increase if the number of runs is increased Proving is carried out according to the acceptance requirements of API MPMS Ch run proving is possible but is not optimal

57 * This method is taken from API 13.2 and 4.8 published in 1994 and 1995 respectively, prior to the formation of the API ultrasonic task group

58 Statistical benefit of designing with a higher target number of runs The benefit of moving from 5 runs to 10 (or more) is significant E.g. the required prover volume reduces by a factor of almost 4 by choosing 10 runs vs 5 runs if designing for a 95% success rate This benefit is related to the statistics only, and is independent of the meter type and performance

59 Improving repeatability

60 Reducing nozzle shaped inlet Substantial diameter/area reduction Beta < 0.64, area ratio < 0.41 Downstream pressure recovery cone for low pressure loss

61 Rapid acceleration of the flow via the smooth contour of the nozzle increases the axial velocity at the measurement section and reduces the relative magnitude of the turbulent features in the flow 8-path measurement in throat

62 RIE - Turbulence reducing flow conditioner Restricts the size of turbulent eddies resulting in higher frequency turbulence and better averaging It has a high porosity and hence a lower pressure loss than a tube bundle

63 Placed at the inlet to the meter

64 Path velocity standard deivation Diagnostic data showing reduction in turbulence 8% 7% Meter with reducing nozzle Meter without reducing nozzle 6% 5% Meter with reducing nozzle and turbulence conditioner 4% 3% 2% 1% 0% Path number

65 Repeatability test data

66 Repeatability analysis Our analysis of repeatability data and prediction of provability is based on assessing the standard deviation of a set of repeats and referencing this to a standard volume of 1 cubic meter s ref s Generally a minimum of 30 repeats is used to ensure statistical significance Can assess the repeatability of any meter type by this method V

67 Full-bore 6-inch, 4-path meter 0.09% Reference standard devation for 1m 3, s ref 0.08% 0.07% 0.06% 0.05% 0.04% 0.03% 0.02% 0.01% API 5.8 (2005) API Ch 5.8 Table B cubic meters 3.3 cubic meters 6.6 cubic meters 10 cubic meters RMS value 0.00% Flowrate (m 3 /hr)

68 6-inch turbine meter Reference standard devation for 1m 3, s ref 0.09% 0.08% 0.07% 0.06% 0.05% 0.04% 0.03% 0.02% 0.01% API Ch 5.8 Table B2 3.3 cubic meters 6.6 cubic meters 10 cubic meters RMS value (Ball Prover) 0.12 cubic meters (SVP) API 5.8 (2005) USM Ball prover SVP 0.00% Flowrate (m 3 /hr)

69 Reference standard devation for 1m 3, s ref 0.08% 0.07% 0.06% 0.05% 0.04% 0.03% 0.02% 0.01% Reducing nozzle & turbulence conditioner API 5.8 (2005) API 5.8 Table B-2 8-path meter with reducing nozzle 8-path meter with reducing nozzle and turbulence condtioner Turbine meter 0.00% Flowrate (m 3 /hr)

70 Direct proving demonstration test

71 Offshore viscous oil export metering The offshore application conditions can be summarised as follows: 5500 m 3 /hr system capacity Offloading temp 30 to 45 deg C Offloading viscosity approx. 100 to 300 cst Nominal flowrate per meter 540 to 2,750 m 3 /hr Reynolds number range approx. 1,600 to 25,000 (offloading plateau at Re in the range 8,000 25,000)

72 Recommendation and demonstration A recommendation of 2 off LEFM 280CiRN flowmeters in 16-inch diameter was made API Ch 5.8 would suggest a prover volume of 83 m 3 for 5 run proving with a 60 % success rate; customer wished to use a normal sized bi-directional ball prover with a round-trip volume of 14 m 3 Demonstration tests were performed for the customer to give confidence that the meter would prove according to our prediction methods

73 System 2 duty and 1 standby streams 30-inch bi-directional prover

74 System No flow conditioner, straight pipe => 5D upstream One filter at inlet to prover 4-way valve Substantial weight and space savings over turbine solution or full bore USM solution

75 Success rate Predicted success rate 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Number of runs

76 Frequency Test results, 120 runs per API 5.8 B % % Meter factor Uncertainty (%) 0.081% 0.054% 0.027% % successful provings % in 6 runs or less No. of runs to achieve +/ % uncertainty

77 Summary and Conclusions Heavy oil applications can be problematical for ultrasonic meters if care is not taken when selecting the appropriate design. Signal attenuation increases with increased viscosity. The provability of full bore meters can be difficult particularly at low Reynolds numbers. Both these issues can be addressed successfully using a Reducing Nozzle meter in conjunction with a turbulence reducing conditioner. Using the appropriate technology Ultrasonic Meters can approach repeatability values more associated with Turbine meters.

78 Questions?