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Recent Advances in Riser Monitoring Systems
Shreenaath Natarajan2H Offshore
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Riser and Conductor VIV
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Why Monitor RisersRisers are fatigue critical structures
Complex interfaces at the vessel and the seabed
Multiple assumptions involved in design data and
methodologiesRiser failure is totally unacceptable
Courtesy: SPE 2005SCR Trench Parted Drilling Riser
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Riser Monitoring System Design
Monitoring PurposeEnvironment / Vessel motion induced riser
responseRiser/soil interactionSpecific component performanceCapture
uncertainties in extreme event responseFatigue concern
Suitable instrumentationData processing requirementsData
communication requirements
Real time / quasi-real time / log & retrieve
CostInstallation
Retrofit / Pre-installation / during riser installation
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Recent Achievements
Cost-effective subsea strain sensorAcoustic data
transmissionSubsea microphone based flexible armour wire
monitoring
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Strain MeasurementFeatures
Conventional electrical foil strain gauges in pressure balanced
cylindrical tubeBending strains along 2 planes3 micro-strain
accuracy
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Strain MeasurementBenefits
3000m depth rating Conventional electrical foil strain gauges
are restricted to above surface / near surface
High resolution suitable to capture small strains causing riser
fatigueExtremely low power consumptionSuitable for both standalone
and real-time applicationsCheapest strain gauge option for subsea
application
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GoM Tahiti SCR Real Time Monitoring System
5 Strain and Motion Sensors Top
11 Strain and Motion Sensors TDZ
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Acoustic LoggingFeatures
Acoustic transponder and sensors powered by self-contained
battery unitAcoustic receiver on deck Software to process and
display on-boardLow power and high precision
accelerometer/inclinometer arrangementElectronics adaptable for any
type of measurements
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Acoustic LoggingBenefits
Acoustic link enables data communication near quasi-real
timeReduces complex cabling and risk of damaging the cablesLow
power electronics minimizes power consumptionAcoustic link enables
data logger switching on/off as required, maximizing the battery
lifeProvides easy retrofit options using ROV/diverOff the shelve
monitoring product
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Mooring Line Monitoring System
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Shell BC-10 Mooring Line Monitoring System
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Flexible Riser Monitoring Features
1D Axial acceleration sensor2D Angle rate and inclination
sensorsMicrophone
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Laboratory Tests
Flexible riser on a test rig to maintain static tension and
apply dynamic tension cyclesArmour wires cut initiated using hand
held tools
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Laboratory Test Results
All 30 wire break tests are recorded by the instrumentation
package
Acceleration Microphone
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Offshore TestsInstalled near the bend stiffener to measure the
background offshore noise detectedArmour wire break noise is
clearly distinguishable compared to:
Background noiseImpact due to dropped objects or collision
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Flexible riser monitoring system
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Conclusions
Low power and more reliable electronicsHigh resolutionCost
effective
Acoustic transmission reducing complex cablingReduced risk of
cable failure compared to a hardwired systemInstrumentation is away
from critical path of installationField proven technology
Novel concept turned in to a realityCapture flexible riser
response near critical riser-vessel interfaceEarly identification
of armour wire rupture
