Fiber Optic Flow Measurement Ole Jacob Velle Optoplan AS

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Fiber Optic Flow MeasurementOle Jacob Velle
Optoplan AS
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Bragg Grating Sensors
Photoimprinted grating
Fiber
core
Input
Transmitted signal
signal
Reflected signal
?
Reflected Spectrum
Strain-induced
P
shift
?
?
B
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Fiber Optic Multiphase Flow Monitoring

• Two-phase, oil/water flow meter available
• Deployed in deep water platform well in GoM
  September, 2000
• Well suited for permanent downhole deployment
• Completely non-intrusive
• Electronically passive, all optical design
• Low profile, integrated with production tubing
• Methodology based on passive listening techniques
  measuring
• Mixture sound speed for phase fractions
• Cross correlation for volumetric flow
• Measurements applicable to 3-phase flow

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Two Phase Fiber Optic Flow Meter
Single fiber optic cable to surface located
interrogation unit

• Full range water fraction
• 20 feet in length
• Inconel 718 construction
• 15,000 psi pressure rating

Flow meter gauges
Pressure and temperature gauges
Standard premium thread connectors
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Two Phase Meter System Overview

• Fluid Properties
• SOS, ? for water oil

P, T
Holdup Calculation

• Phase flowrates
• Homogeneous Model

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Speed of Sound Measurement

• Utilizes passive listening techniques from
  multiple sensors to extract speed of sound from
  production generated noise
• Link between speed of sound and phase fractions
  is well known
• Low frequency/long wavelength, i.e. tolerance to
  inhomogeneities

Example Oil Water Mixture
5000
4800
4600
Mix. sound speed (ft/sec)
4400
4200
4000
0
10
20
30
40
50
60
70
80
90
100
Volume fraction water ()
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Oil and Water Sound Speed Contrast
6000
Produced water
5500
SOS contrast
5000
Sound speed (ft/sec)
4500
Reservoir oil
4000
3500
Bubblepoint pressure
3000
0
2000
4000
6000
8000
10000
12000
14000
Pressure (psia)
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Bulk Velocity

• Cross-correlation based volumetric flow sensor
• Completely non-intrusive, non venturi-based
  design
• Sensor tracks production generated pressure
  disturbances
• Equivalent performance in single and multiphase
  flows

50 Water / 50 Diesel Mixture
100 Diesel Oil
6000 BPD
6000 BPD
Cross correlation function
Cross correlation function
Location of peak determines time delay
0
0
Time lag (sec)
Time lag (sec)
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Flowloop Test Results
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Error Analysis Water fraction Mean
1.5 s3.0 Volumetric Flow Mean 0.1 s6.2
Solid Reference Open CiDRA
50
Orientation
40
90
80
Water flow rate m3/h
45
30
10
0
-2
20
10
0
0
10
20
30
40
50
60
Oil flow rate m3/h
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3-phase Flow Measurement Capability

• Combining existing technologies
• 2-phase meter from Cidra/Optoplan
• Idun from FMC Kongsberg Subsea -
• software interpretating sensor data to establish
  flowrates
• Demo2000 project with Norsk Hydro, TotalFinaElf
  and BPAmoco

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Idun

• Utilize flow related data from sensors
  distributed along the wellbore
• Constitutes an interface between sensors and
  physical models
• Search algorithm adjusting pure phase flowrates
  to match measured data from sensors

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Idun visualized
Initiate at P1 and T1
2
ù
é
-
X
X
å
Err
i
,
c
i
,
m

w
ú
ê
i
X
ú
ê
û
ë
Initial guess phase rates
i
i
,
m
WH
P2
Vector search new rates
Calculate trajectory

SOS
No
P1,T1
OK?
Qoil
Qwater
Qgas
Accept and store results
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Numerical study

• Ideal artificial sensor signals generated with
  Idun
• Add noise to ideal signals based on sensor
  performance specs.
• Feed noisy signals back to Idun to calculate
  rates

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Oil
15
Water
16
Gas
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Flowloop Test

• Demonstrate current 2-phase meter performance
• Demonstrate performance of fiberoptic sensors in
  combination with Idun
• Targeted for May 2001

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Summary

• All fiber optic two phase meter available
  (oil/water)
• Demonstrated in flowloop tests
• Installed in GoM
• Fundamental measurements applicable to multiphase
  flow with slip
• Extension to 3-phase flow by combining
• 2-phase meter sensors
• Idun (interpretive model)
• Flowloop test to be conducted May this year to
  demonstrate 3-phase capability with optical
  sensors