Optical Sensing Systems Gisle Vold. © 2006 Weatherford. All rights reserved. Slide 1 1870 : Principle of Total Internal Reflection discovered 1950

Optical Sensing Systems

Gisle Vold

Slide 2© 2006 Weatherford. All rights reserved.

1870 : Principle of Total Internal Reflection discovered

1950 : Invention of first laser

1970 : First low-loss fibre produced

1974 : Launch of optical communications

1986 : Introduction of optical amplifiers

1994 : Introduction of multi-wavelength systems

2000 : Peak of Telecom bubble

History


Transmission Data Rate and Capacity

• Broadband capability of optical fiber allows multiple channel transmission

– Currently 128 channels with existing components

– Each channel can carry 10Gb/s

– Unlike electrical signals, optical signals do not interfere with each other

• Each Fiber has an aggregate data rate of 1.28Tb/s = 1,280,000,000,000 bps !

• This translates to:

– 20 million simultaneous phone connections (64kb/s each); typical telecom twisted-pair cable 300 phone calls

3

Twisted Pair Copper- MHz - 300 Phone Calls

Single Fiber - THz - Over 20 Million Phone Calls


Bandwidth !


What makes us different ?

• Operation Principle

• Suite of Sensors

• Extreme Long Term Stability

• Unmatched Durability


Bragg Grating Operating Principle

Input SpectrumInput Spectrum

P

Transmitted SpectrumTransmitted Spectrum

P



UV interference

UV laserbeams

photo-inscribedgrating in core



Reflectedcomponent

Transmittedlight


P


P

B

Reflected SpectrumReflected Spectrum

P

B



stretch

Strain-inducedshift in grating

resonance wavelength


Reflectedcomponent

Transmittedlight


P


P

B

Reflected SpectrumReflected Spectrum

Pstrain-induced

shift

B



-5

-4

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-2

-1

0

1

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0 2 4 6 8 10 12 14

Time (au)

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lati

ve

In

ten

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Optical Wave 1

Optical Wave 2

Interference of 1 + 2

Interference of Two Optical Waves


-1.5

-1

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Time (au)

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Time (au)

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-1.5

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Time (au)

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Path 1

Path 2

=2**n*L

=2**n*L

L2-L1

Bulk-Optic Michelson Interferometer


Mirrors

Two Legs with Mirrors

Fiber Michelson Interferometer


Single Leg with Grating Reflectors

Fiber Michelson Interferometer


What makes us different ?

• Operation Principle

• Suite of Sensors

• Extreme Long Term Stability

• Unmatched Durability


The Case for Fiber Optic Sensors

• High Reliability

– No Downhole Electronics

– No Moving Parts

– Nominal Part Count

• Ideally Suited For Harsh Environments

– High Temperature Capability

– Vibration and Shock Tolerant

• High Data Transmission Capability

– Multiple Sensors on Common Fiber Infrastructure

– Technological Advances Driven by Telecom


Downhole Cable


Temperature Profiling

• Thermal profile of well

• Production and injection profiling

• Identify well problems

• Monitor water, gas, steam breakthrough

• Artificial lift monitoring

• Distributed Temperature Sensing (DTS) and Array Temperature Sensing (ATS)

0

400

800

1200

1600

2000

2400

2800

3200

0 20 40 60 80 100 120

Temperature

Perforated Interval

Distributed Sensor

Continuous Sensor

Distributed Sensor

Continuous Sensor

Quasi-Distributed Sensor

Array Temperature Sensor

Quasi-Distributed Sensor



DTS - Operation Principle

Spectrometer

Laser

source

Processing

Spectral

Processing

T(z)

Fiber

T

e

m

p

e

r

a

t

u

r

e

P

r

o

f

i

l

e

T(z)

Scattered light at location z

Pulse

Modulator

Raman Stokes/Anti-Stoke Ratio

Surface Unit


Raman StokesAnti-Stokes ratio

DTS – measurement principle


Array Temperature Sensing

• Accurate/stable point measurements– 15-18 points/fiber– P/T gauge can be deployed on same

fiber• 1 P/T + 12 ATS

– <0.01°C (0.018°C) temperature resolution

– Update rate 3 – 5 seconds• Similar technology to Weatherford optical

P/T gauge– Glass microstructure– Manufactured by Weatherford– Integrated into standard ¼” Inc 825,

3-fiber cable• Temperature sensor isolated from strain• Standard deployment techniques

– Location of sensors needs to be defined in advance of installation

• Same instrument as optical P/T gauge (platform or subsea)

• Long distance (>30km) reach• Field trials planned for 2006 (land) and

2007 (subsea)

Leveraging Existing Technology



Build model to evaluate DTS sensitivities to :

• total flow rate

• oil, gas and water profile differences

• flow allocation

• water breakthrough

• gas coning

• pressure drawdown

Specific input required from customer

Simulation of well candidates


• WFT-PLATO software

– Three-phase PLT analysis

– Statistical optimization

– Global statistical modeling of entire well

– Automatic determination of flow regime

– Interactive visualization

– Simultaneous use of all logs and surface information to determine production profile

– Emulation capabilities

• Temperature Profiling Design & Analysis

– Warm-back tests for injectors

– Specialized tests for producers

– Temperature array array design

– Service

– Software

WFT Temperature Profiling Analysis Capabilities


Temperature Profiling Data Viewer

• Standalone application for viewing DTS data

• SQL Database, LAS, POSC, ASCII format files

• Features

– Animations relative to baseline DTS data

– User-specified data interval density (in time)

– User-settable zooming, scaling, gridding, scrolling, smoothing, etc.

• Intended users

– Operators – for quick qualitative analysis

– Production and reservoir engineers – for identifying trends and visualizing specialized tests, e.g., warmback tests in injection wells


Why Measure Flow Downhole

• Reduce surface facilities and well tests

– Eliminates the need for test separator

– Handling of high gas rates

– Favorable measurement conditions

• Allocation from/to multiple zones

– Production and Injection well applications

– In multi-zone and multi-lateral completions

• Commingling

– Regulatory requirements

• Faster identification of production anomalies


Weatherford’s Optical Flowmeter

• Measurements

– Flow velocity (gives volumetric flow rate)

– Speed of sound (gives gas volume fraction)

• Measurement Advantages

– Liquid, gas, or multiphase

– High accuracy:

• single-phase ±1%

• multiphase ±5%

– Zero drift

– Bi-directional flow rate

– High turndown ratio, scalable to any pipe size

Turndown Ratio is the ratio of the highest to the lowest measurable flow rate

Turndown Ratio is the ratio of the highest to the lowest measurable flow rate


Weatherford’s Clarion™ In-Well Seismic System

• High Performance– Broad bandwidth, high sensitivity and

wide dynamic range

• Optical Seismic Sensors– 3-component accelerometer

– hydrophone (prototype only)

• Standard Weatherford optical backbone

– Combines with optical PT, DTS & Flowmeter

• Dry tree solutions available

– Subsea under development

ALL OPTICAL SYSTEM

LIFE OF FIELD RELIABILITY

Life of Well Seismic™


RUGGEDIZEDSENSOR CARRIER

3-C SENSOR

Clarion™ Deployment in Production/Injection Wells

ARRAY SPOOLING UNIT

SENSORMANDREL

Tubing or casing conveyed



Geophysicists (benefit)

• Permanent Measurement Repeatability

• Real time on demand seismic data

• Passive event gathering

• Active Seismic event Gathering

• Calibration of Seabed Sensors

• Intended Wellbore viewing

• High resolution Imaging in 4D Timeline

• Geometry understanding

• Inversion – Porosity/ Resistivity

• Fluid Movement understanding

• Fracture Delineation

• Bypass Pay

• Cap Rock Integrity



Reservoir Engineers (Benefit)

• Available with P/T, Flow and DTS systems

• Material Balance help

• Formation Activity

• Fracture Tracing

• Cross Flow

• Well Balance when shut in

• Reservoir Loss path

• Reservoir Boundaries

• Injection performance

• Interference Test greater understanding

• Uncertainty reduction



• Drilling Engineer (Benefit)

• Infill well placement

• Real time seismic while drilling

• Look ahead Drilling

• Production Engineer (Benefit)

• Stimulation


1990’s DTS installations

1993 First In-well Optical P/T Gauge

1996 First Subsea Optical P/T Gauge

1999 First In-well Bragg Grating P/T Gauge

1999 First In-well Seismic Accelerometer

2000 First Non-intrusive In-well Fiber Optic Flowmeter

2001 Optical P/T Gauge and DTS in Single Completion

2002 Multiple Optical P/T Gauges in Single Completion

2003 Full 3-phase Fiber Optic Flowmeter with P/T Gauges

2003 Multi-zone Optical P/T Gauges and Remote Flow Control

2004 Multi-zone Optical P/T Gauges and Flowmeters with Remote Flow Control

2004 Casing-conveyed, Multi-station, Seismic with P/T Gauge

2005 Multiple Optical P/T Gauges and DTS Integrated with Sand Control

2006 Offshore Tubing-conveyed, Multi-station, Seismic with P/T Gauge

In-Well Optical Sensing Chronology

WORLD-FIRST DOWNHOLE FIBER OPTIC INSTALLATIONS:

Documents

Optical Sensing Systems Gisle Vold. © 2006 Weatherford. All rights reserved. Slide 1 1870 : Principle of Total Internal Reflection discovered 1950