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DUALSTREAM Elite Follows the concept of existing Dualstream family - simple, robust, and with corrosion and erosion, hydrates, sand, salinity in mind. IS more sophisticated solution yet small and compact Designed to meet the requirements on accuracy and sensitivity across a wide range of GVF ( cover 99% of Gas condensate field requirements) – work in both oil and water continuous flow AND Reduce the reliance on PVT
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How it works… Dualstream Elite
This meter utilizes Solartron’s wide experience of DP flow metering, combined with a microwave water fraction meter to accurately determine all three phases: gas, condensate and water.
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Pressure and DP from the Venturi
The Pressure and Differential Pressure Measurements come from the Venturi meter, allowing an approximation of the gas flow rate.
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Microwave water fraction measurement
The Water Fraction sensing section is used to determine the liquid flow rates…
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Temperature…and compute
…which in combination with the Pressure and Temperature provides corrected flow rates for all three phases.
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Algorithm - Inputs So, detailing the algorithm in a slightly different way… First we have the transmitter and water fraction meter inputs, where the water fraction meter includes electronics to process the raw signals into a useable measurement.
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Algorithm This data is then all passed back into the flow metering algorithm.
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Algorithm – Reduced PVT Reliance
Data is also needed based upon the composition of the fluids passing through the meter. The Dualstream Elite has a reduced reliance on this PVT data, as we will show later in this presentation, hence being shown here with dashed lines.
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Algorithm – Reduced PVT Reliance
The output from this meter includes the water fraction…
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Algorithm Outputs …as well as the corrected wet gas flow rates.
This diagram removes the iterative steps, but should indicate that this instrument is based upon robust flow metering methods that have stood the test of time and utilizing more recently developed techniques to improve the accuracy and sensitivity of the measurements. The next few slides will detail aspects of the development process for this meter…
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Microwave Resonance The Water Fraction meter sets up resonance conditions in a cavity through which the liquids and gas passes, where a microwave signal is used to “drive” it. In the same way that changing the atmospheric conditions would affect the child on the swing, changing the fluids passing through the meter alters the resonance condition in a measurable way. Physical structures called mode conditioners are included within the walls of the cavity, which serve to enhance the measurement signals we wish to measure, and reduce those that would affect these signals, further improving the meter’s ability to accurately measure the conditions encountered. UNIQUE POINT – NON INTRUSIVE SENSORS
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In Theory… The theory demonstrated that practical metering techniques could be developed – for instance, in this simplified plot it is clear to see that for changing water fraction a trend can be determined – these are the dashed lines at the top. The effects of salinity can also be seen by looking at the solid lines below, which have lower amplitude and greater peak width, but still exhibit the same trend in peak position.
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…and in Practice Thankfully, early experiments demonstrated that the theory would work in practice! This data (taken over part of the range of liquid fractions shown in the previous slide) shows the same clear trends, indicating that this should allow for a useable metering technique.
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In-house Research and Simulations
This has meant that we have been increasingly able to simulate and then to test the conditions that the meter will encounter. Different effects have been evaluated, such as flow profile, salinity, and temperature – all the kinds of things we talked about earlier on - and characterising these have led to improvements in the meter’s design and algorithm. For instance, although the fundamental principles of the meter have not changed, changes have been made to the physical attributes of the meter to make it more sensitive, responsive and reliable…
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DUALSTREAM ELITE So the Dualstream Elite has been designed to be accurate, sensitive and robust, either for Topsides or Subsea applications, in either horizontal or vertical down configuration, with the patent-pending microwave resonant cavity, non-wetted microwave sensors and integral mode conditioners to enhance the electromagnetic signals we want to measure. It is a sophisticated device, based upon relatively simple operating principles, just as we have said is often the case for modern wet gas flow meters.
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(Uncertainties specified to 95% confidence)
Design Specification For: Operating Range: 90% – 100% GVF Water to Liquid Ratio (WLR): 0% – 100% Gas Mass Flow Rate: ±2% relative (typical) Water Volume Fraction: ±0.10% absolute Condensate Mass Flow Rate: ±10% relative (Two-Phase mode) (Uncertainties specified to 95% confidence) The Dualstream Elite was designed to meet the specification detailed in this slide: For up to 10% liquid by volume, where the water can be any fraction of the liquid, the gas will be known to 2% relative, the water volume fraction to 0.1%, and currently the condensate flow rate to 10% relative. In order to meet this specification we have had to carry out a wide range of testing.
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Wet Gas Testing This has included wet gas testing at a number of 3-phase loops, such as CEESI in Colorado and the South West Research Institute in Texas. Wet Gas test data has been taken over the full range of water fraction and a wide range of GVF to assist in the further development of the mathematical algorithms.
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(red lines indicate target specification)
Gas Mass Flow Rate Accuracy As part of some testing at CEESI we also took some validation data, which was also over the full range of water fraction, but only over a range of 97.5% to 100% GVF due to time and budget constraints of this portion of research testing. This data has not been used to develop the flow metering algorithms, but instead is solely utilized to validate them. This graph, and the one that follows, details some of the data in this range used for generating the algorithms (which are the hollow points on the graph) along with the 30 validation points (shown as the solid points). The data here is at two distinct pressures – shown by the different shapes - and also at multiple water cuts between 0 and 100%. This 0% line represent the reference conditions – and therefore each point show the deviation of the meter’s output reading from this baseline. The red lines also indicate the flow meter’s target uncertainty specification as detailed earlier on – so we would like the points to all be within these lines. You can also see that the testing was carried up to very dry gas – up to 99.8% gas volume fraction for the validation points, and 100% for the algorithm data. From this data it is clear that the algorithms resolve the gas mass flow rate for the validation points well within the targeted accuracy of 2%, as we had hoped. CEESI data verifying the Gas Mass Flow Rate accuracy for Dualstream Elite (red lines indicate target specification)
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(red lines indicate target specification)
Water Volume Fraction Accuracy Likewise, this second slide – again showing the algorithm data alongside the data for all 30 validation points – clearly shows that the water volume fraction is generally well within the 0.1% we were aiming for. This indicates that the determination of the water volume fraction is very accurate across the full range of the meter, even at very dry gas conditions. CEESI data verifying the Water Volume Fraction accuracy for Dualstream Elite (red lines indicate target specification)
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(Uncertainties specified to 95% confidence)
Flow Meter Specification Achieved For: Operating Range: 90% – 100% GVF Water to Liquid Ratio (WLR): 0% – 100% Gas Mass Flow Rate: ±2% relative (typical) Water Volume Fraction: ±0.10% absolute Condensate Mass Flow Rate: ±10% relative (Two-Phase mode) (Uncertainties specified to 95% confidence) This data clearly validates the uncertainty specification for the meter shown earlier. However, in the two-phase mode of operation (where the CGMR is given as an input to the flow meter) it is unfair to see this as a validation of the condensate mass flow rate. [If we had, the uncertainty would have been similar to the values seen for the gas mass flow rate, given that we know the CGMR]. Instead, later slides will look give the sensitivity of the meter to an error in the condensate to gas mass ratio, which can be considered to be a more “real world” perspective.
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Two Modes of Operation A two-phase mode, requiring knowledge of the condensate content from EOS and PVT A three-phase mode in which condensate content is derived independently of EOS (future) The remainder of this paper details the performance of the two-phase mode, where some input from an Equation of State PVT model is required. However, as we have hinted at and now hope to show you, even in this mode there is a reduced reliance on the parameters from these calculations. The three-phase mode will hopefully be detailed at a later date in a future paper, which operates by finding the condensate content without requiring PVT modelling from a total hydrocarbon composition.
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Gas Volume Flow Rate Sensitivity to 10% Error in CGMR
The next few slides detail a sensitivity analysis of the 2-phase mode. This has been carried out to be directly comparable to a similar analysis provided by another wet gas manufacturer. Each of the next six graphs shows the same range of gas volume fraction and water liquid ratio, representing the specified operational region of the meter. This graph indicates that for a 10% change in the CGMR, an error would be seen in the gas volume flow rate of less than 2% for much of the operational region, and only up to 3% in the region with most condensate – as would be expected.
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Water Volume Fraction Sensitivity to 10% Error in CGMR
Likewise, an error would be seen in the water volume fraction of less than 0.1% except in the regions of high liquid content, where the relative error becomes more meaningful…and is still very small.
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Hydrocarbon Mass Flow Rate Sensitivity to 10% Error in CGMR
As would be expected, a change in CGMR has an effect on the overall hydrocarbon mass flow rate. This would obviously include the effects on the gas flow rate, as shown in the first of these graphs. Similarly to that slide, the effects are reasonably small, especially given the significant input variation.
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Gas Volume Flow Rate Sensitivity to 5% Error in Gas Density
The effect of the change in gas density by 5% is mainly due to the alteration made to the venturi differential pressure calculation, thus altering the gas volume flow rate. It also has an effect on the algorithm parameters characterised by gas density, but these effects appear to partially compensate for one another. Therefore the overall effect is generally less than 3% across the entire region of meter operation.
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Water Volume Fraction Sensitivity to 5% Error in Gas Density
Again, the sensitivity of the water volume fraction to the gas density is small, with errors of less than 0.1%, apart from the regions of high liquid or high water content where the relative error would again be more relevant.
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Hydrocarbon Mass Flow Rate Sensitivity to 5% Error in Gas Density
And again, as would be expected, a change in the gas density has an effect on the overall hydrocarbon flow rate…
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Flow Meter Sensitivity
In summary of the last six slides, what we have hoped to show is that the meter’s sensitivity to significant changes in CGMR or gas density is typically within the uncertainty specification. In other words, as the changes to gas density and CGMR represent errors in the PVT parameters, these graphs demonstrate that the meter has a reduced reliance upon PVT data, as we said it would be for the two-phase mode.
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Meter must cope with saline water in oil
Water salinity Meter must cope with saline water in oil and water continuous conditions It is desirable to have a real-time measurement of salinity As the development of the meter moves on, other more complex issues must be considered. One are in which we have been making progress is water salinity.
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Salinity 3.5% by mass of NaCl
Data from SwRI 2009 at 135bar 3.5% by mass salinity is approximate to the salinity of sea water. Peak amplitude drops due to the salinity of the water. Resonant peaks can still be resolved at high water/liquid levels.
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Salinity 8.1% by mass NaCl Again at 135bar
Salinity now more than doubled to 8.1% by mass. Peak amplitude suppressed much more than that at 3.5% salinity but peaks still resolvable.
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Comparison between 3.55 and 8.1% salinity
Peak amplitudes much reduced at the higher salinity. Peaks still well defined and straight forward to resolve.
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Amplitude depends on water salinty
Explore the relationship between salinity and peak amplitude. Water volume fractions range from zero to over 6% Provides the potential for direct measurement of salinity. This data for 90bar (65kg/m3). Except for the CEESI data at ~ 58kg/m3 which is added for illustration
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And at higher gas pressure
Same as previous slide but at a higher pressure – 135bar Again water volume fractions from 0 to over 6%
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Viewed at different pressures
Summary showing the difference between 3.5% and 8.1% salinity for 90bar and 135bar Water volume fractions from around 0.5% to over 6%
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3 Phase – water continuous
3-phase data from SwRI This data taken at 135bar. Water and liquid volume fractions in range 0.5% to over 6%
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3 phase – water continuous
Fewer points than for 135bar but trends still clear
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3 Phase – water continuous
Blue points 135bar, red points 90bar. Solid points 3.5% salinity – hollow points 8.1% salinity
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3 Phase – oil continuous Much more complex than for water continuous. There is a dependence on water liquid ratio, which increases the scatter as we don’t have a regular pattern of WLR.
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Subsea (Preview) Dualstream Elite
Qualification In accordance with DNV–RP-A203 Performance Specification as per topside version Low Power Fully redundant sensors/electronics 3000m / 10,000 psi design Vertical or horizontal installation Qualification scheduled to be completed in Q1 2012
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SUBSEA ELITE Reliability
Subsea (Preview) Dualstream Elite SUBSEA ELITE Reliability Electronics Module Available Protocols Modbus Canbus (SIIS level 2) IWIS (Ethernet SIIS L3 during 2012) Fully redundant PT,P and T sensors Fully Functional ‘Standby’ Electronics Enclosure Multiple water fraction sensors ‘built in redundancy’
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Summary Dualstream Elite
Technology build on 20 years experience in wet gas measurement Designed to specifically meet the requirements of wet gas fields Provides highly accurate measurement for reservoir engineers EXPERTISE years experience, tried and tested Dualstream, 200 plus projects, new meter is build on that knowledge SOLUTION - Designed to cope will full range of wet gas fields, oil or water continuous , Wide Operating Range in both water and oil continuous flow regimes MEASUREMENT - very accurate gas and water rate. Improve production, detect water breakthrough to help mitigate hydrates, or allocate production
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