Performance testing of a novel Fibre Optic based vortex flow meter Smart Flow

Transcription

1 Performance testing of a novel Fibre Optic based vortex flow meter Smart Flow in high pressure wet steam by R. Jansen, TNO, The Netherlands J. Golliard, TNO, The Netherlands C. Staveley, Smart Fibres Ltd, UK W. Schiferli, Shell, The Netherlands A. Znotins, Shell, Canada

2 Content Market need The solution Measurement principle Test results Air/Water (water wet air) Test results Wet steam (condensed steam) Conclusion Way forward

3 Market need Availability of a cost-effective solution for permanent flow and quality monitoring of steam injected into steam injection wells using specific advantages fibre optic sensing

4 Solution; combination of: Existing principle, vortex meter; Proven technology Robust and low cost Fibre Optic (FO) sensing element; Implemented existing FO architecture Using specific advantages of FO

5 Vortex meter principle Vortex shedding behind bluff body Shedding frequency linear to flow velocity Vortex shedding frequency Strouhal number U Sr D 0 f = velocity bluff body diameter

6 Fibre Optic Vortex Meter

7 Fibre Optic (FO) Element FO sensor inside vane Fibre Bragg Grating (FBG) Reflected wavelength varies with strain (and temperature) Alternating bands of high and low refractive index

8 Multiplexing FBG Sensors

9 Measured parameters Vortex shedding peak Mechanical eigenfrequency vane Required dynamic range: > 2500 Hz

10 Test result single phase gas

11 Performance two phase flow? Gas hold-up actual gas velocity increases also known as over reading Possible interference liquid layer Presence of droplets: in the flow near the vortex meter deposited on the shedder bar

12 Expected Flow regime In surface steam pipelines Superficial liquid veloc city [m/s] Superficial gas velocity [m/s]

13 Two clear mechanisms Based on experiments: Interference liquid layer quality factor vortex shedding -3dB width vortex Q vp f = v f -3dB Droplets changing the effective gas density Shift in mechanical eigenfrequency

14 Test results two phase Air/water Wet steam

15 Test results air/water

16 Air only (no water)

17 Liquid hold-up (quality factor)

18 Liquid hold-up (mech. eigenfr.)

19 Test results wet steam

20 Dry Steam

21 Wet steam test conditions Entrained frac ction [-] bar 80 bar 120 bar True Usg [m/s]

22 Actual steam vapor flow The measured vortex shedding frequency is translated to a vapor flow rate: Assuming single phase gas Using measured steam quality (based on the vortex peak quality factor) Known liquid hold-up based on two phase flow simple model (derived from OLGA) Assuming two phase flow to calculate the (corrected) actual vapor flow rate

23 Assuming single phase flow SteamQuality < True Usg [m/s] Error (measured-reference)/reference [%]

24 Known quality & simplified model SteamQuality < True Usg [m/s] Error (measured-reference)/reference [%]

25 Measured quality (quality factor)

26 Assuming two phase flow using: Measured quality & simplified model Error (measured-reference)/r reference [%] True Usg [m/s]

27 Conclusions wet steam High steam quality (>0.98) errors in flow: less than 3% for velocities above 7 m/s between 2 and 7 m/s errors less than 5% Lower steam qualities (<0.98) errors in flow: increased to 60% without correction With steam quality correction: less than 10% for velocities above 7 m/s between 2 and 7 m/s less than 20%

28 Way forward Test performance under field conditions: Steam tests only covered end of life field conditions in Shell Canada No (affordable) test rig can deliver such high flows Bench mark field test: steam test separator Mature and further validate technology: Test robustness current algorithms field conditions Improve current algorithms to reduce steam quality errors down to +/- 10% (currently +/- 20%)

29 Back-up slides Slide 30: Over-reading as function of XLM Same plot as shown in slide 23 Slide 31: Measured steam quality taken into account field conditions Shell Canada (Usg > 7 m/s). Note: Nominal field velocities (10 < Usg < 15 m/s)

30 Assuming single phase flow Over Reading versus XLM Wet gas region 0 XLM < 0.3

31 Measured quality (quality factor) Usg > 7 m/s (field conditions) error lines +/- 20%