FiberOptic DownHole Sensing:

1
Fiber-Optic Down-Hole Sensing

• A Discussion on Applications and Enabling
  Wellhead Connection Technology

SPE/OTC Paper 18121 Perry Joseph Wright Willard
Womack, Ocean Design, Inc 2006 Offshore
Technology Conference, Houston, Tx
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Economic Drivers for Intelligent Wells

• The growing shortfall between forecast demand and
  recoverable reserves, requires that the Offshore
  Oil Gas Industry optimize recovery.
• Historical average production of oil in place
  35
• Intelligent or Smart Well Technologies permit
  near real time well control
• Projected recovery using Intelligent Well
  Technologies 50 - 60

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Intelligent Wells Technologies

• Intelligent or Smart Well Technology is targeted
  at
• Increasing production total recovery
• Reducing CAPEX, OPEX and operating Risk
• This is achieved using
• Flow control
• Feed through isolation packers
• Control communication
  power cables
• Down-hole sensors
• Surface data acquisition control
• Wellhead optical electrical penetration systems

4
Review of Fiber Sensors in Oil Gas
1999 Weatherford develops First Subsea Optical
P/T Gauge
2000 SENSA (SLB) Installs first permanent DTS
Monitoring System in Shell Expro TA-27 Gas Lift
Well
2002 Norsk Hydro Installs first system containing
multiple FO pressure and temperature gauges in a
single well at Oseberg east E-11C in North Sea
1978 FBG Proposed by Hill
Early 1990s Schlumberger uses point sensor
Spectroscope to monitor oil composition in ground
2001-2005 ODI develops the HT/HP I-Conn Wellhead
Penetration System for use in Vertical
Horizontal x-trees and Down-hole
1999 Weatherford integrates first permanent
FBG-based optical sensor
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Fiber Sensors

• There are a number of different optical sensors
  that have been deployed, but they fall into two
  discrete categories
• Point source sensors
• Fiber Bragg grating sensors
• Mechanical point source sensors,
  where a change in a machined part
  is read using the optical signal
• Distributed sensors
• DTS Distributed Temperature Sensing
• DTSS - Distributed Temperature Strain Sensing.
  (Similar to DTS, with the addition of strain
  measurement)

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Distributed Temperature Sensing - DTS

• DTS technology uses one of the light scattering
  properties (Raman scattering) of the optical
  fiber that allows the temperature of the fiber to
  be measured along the length of the fiber.
• Range 10 km
• Spatial Resolution 1m
• Thermal Resolution 0.1ºC

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Fiber Bragg Grating

• Bragg gratings are sensitized short lengths of
  fiber that allow measurement of the change in
  length of that section of the fiber
• Multiple gratings can be placed on each fiber in
  series or in parallel
• These sensors can be used to measure
• Temperature
• Pressure
• Strain
• Vibration

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System Performance Vertical X-Trees

• The vertical tree penetration system includes
• External bonnet penetrator on BX 150 flange
• Lower valve block penetrator
• I-Conn compliant mount assembly
• I-Conn wet-mate valve block receptacle connector
• I-Conn wet-mate tubing hanger plug connector
• Dry mate tubing hanger receptacle connector
• Dry-mate plug connector on gauge cable

Dry-mate receptacle
Dry-mate plug
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System Performance Horizontal X-Trees

• The vertical stab horizontal tree penetration
  system includes
• Subsea ROV wet-mate optical connector
• ROV installable compliant stinger assembly
• Guide funnel
• I-Conn wet-mate receptacle connector
• I-Conn wet-mate tubing hanger plug connector
• Dry mate tubing hanger receptacle connector
• Dry-mate plug connector on gauge cable

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System Performance Running Tool

• The landing string assembly needs many more
  connections and penetrations in various
  configurations than a tree system including
• Workover umbilical termination
• Umbilical termination to landing string jumper
• Upper landing string dry-mate connector
• Fiber management in one or more locations
• Optional subsea test tree to landing string
  I-Conn wet-mate connector
• Lower landing string to tubing hanger running
  tool I-Conn wet-mate connector
• Lower tubing hanger running tool to tubing hanger
  I-Conn wet-mate connector
• Optical losses could exceed 3.2 dB, but is offset
  by having the vessel vertically above the well.

Subsea test tree
Landing string
Tubing hanger running tool
Tubing hanger
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Connector Specification - IWIS

• The IWIS joint industry project is writing
  standards for operation and qualification of
  optical (and electrical) tree penetration
  systems.
• API/ISO standard 13628 Petroleum
  and natural gas industries. Design
  and operation of
  subsea production systems,
  Part 6 Subsea production
  control systems.
• Draft standards submitted to IWIS
• The standards offer minimum
  performance and qualification
  requirements for optical tree
  penetration hardware.

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Basic Qualification

• Optical Performance Tests
• Optical Performance lt0.5 dB IL -30 dB RL
• Mate Tests Turbid aligned and misaligned mates
  at 6,000 psi
• Extreme Temperature Pressure 15,000 psi at
  130ºC
• Materials Tests
• Materials compatibility
• Environmental Tests
• Hydrostatic Tests 15,000 psi
• Thermal Cycle, Shock Storage Tests
  130ºC to -40ºC
• Shock Vibration 3x, 30G, ½ sine, 11ms,
  6-axis 1-150 Hz, 5G, 3-axis.
• Gas Leak Test 1,000 psi helium
• Long-Term Creep Test 15,000 psi 130C
• Third Party Tests
• ROV Mate Test (at SWRI)

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Summary

• The recent SPE conference in Galveston In-well
  Optical Sensing - Subsea Well Applications - Are
  We Ready? addressed the issues surrounding
  uptake of optical fiber as part of the
  intelligent wells technologies.
• The conclusion was that in general the technology
  is ready for systems trials, but that the
  commercial advantages are still to be proven.
• The I-Conn wet-mate connection system for
  vertical and ROV stab horizontal systems is being
  reviewed for re-qualification to 20 kpsi
  operating at 177º C