challenges of ‘deep’ water to jackup conductors and risers · challenges of ‘deep’ water to...

Challenges of ‘Deep’ Water To Jackup Conductors And Risers

Alex RimmerEngineering Team Leader, 2H OffshoreSubsea Europe14-15th November 2011

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3

Overview

What is ‘deep’ water for jackup rigs?Jackup conductor/riser arrangementsWhat are the limitations in ‘deep’ water?How do we overcome the limitations in ‘deep’ water?

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What Is ‘Deep’ Water For Jackup Rigs?

>>80M

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Jackup Conductor/Riser Arrangements

JackupAccess/tensioning deckConductorSurface wellheadSurface casingSurface BOPOvershotDiverterCasingsPull-up tensionerPush-up tensionerTemplateMudline suspension (MLS)Subsea housing/wellheadFull-bore HP drilling riser

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What Are The Limitations In ‘Deep’ Water?

System doesn’t scale well – increased jackup & riser deflectionsLimited ‘deep’ water experience in harsh environmentsHigh pressure typically requires large BOP – very stiff

L

L

BM BM

<<80m >>80m

limit

limit

50 Year Wave + Current

Large jackup motion

Small jackup motion

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Rotary Table

Diverter

Top of Overshot MandrelOvershot PackerOvershot Mandrel

Annular BOP

BOPBOP Adapter

CTU Deck

Tension Joint

Bottom of hull

MSL

Lower Stress Joint

Wellhead Connector

Tree

WellheadTemplate

Mudline

30 x 1.5" Conductor (1st ST2 Connector)

(Bottom of Model)

Tension Ring

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Conductor and Riser Design IssuesConductor/riser joints through tensioner (>1.0 σy, fatigue, >connection capacity)Conductor/riser joints above subsea wellhead (>1.0 σy, fatigue, >connection capacity)Connections to wellhead, tree and BOP (> capacity)Conductor joints below subsea wellhead (>1.0 σy, connection capacity)*Overshot lateral load (~40-60Te)Lateral load on tensioner and/or tension deck (~80-120Te)Overshot rotational lockup (0.5-5deg) induced load

* Generally improved compared with semi-submersible for subsea well with HP riser

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How Do We Overcome The Limitations In ‘Deep’ Water?

Reduce conservatism in analysis methodologies

Riser operational procedures

Design changes to riser and vessel

Integrity Management

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Reduce Analysis Conservatisms

>30% improvement in response achievable

Original

BM

Reduced Conservatism

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Riser Operational ProceduresDe-pressurise (plug/water fill) – improve system capacityDisconnection of overshot mandrel

L

BM

50 Year Wave + Current

Large deflections/rotations

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Design Changes

RiserVIV suppression – strakes, fairingsSecondary tensioner systemsFlanged riser connectionsFlange bolt material grade and preload increaseLocalised wall thickness and material gradeIntegrally forged jointsFlexible overshot mandrel

VesselIncrease rig load capacities

Vertical - cantilever/tension deckLateral - tension deck/overshot

Floating diverter

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Integrity Management

Instrument riserDefine integrity management planDefine key performance indicators (KPI) to assess response against

Green = no action requiredOrange = evaluate responses furtherRed = inform operator

immediately

Determine if measured responses match predicted responses

Validate analysis modelsCalibrate riser models if requiredRedefine KPI’s if required

Rotary Table

Diverter

Top of Overshot MandrelOvershot PackerOvershot Mandrel

Annular BOP

BOPBOP Adapter

CTU Deck

Tension Joint

Bottom of hull

MSL

Lower Stress Joint

Wellhead Connector

Tree

WellheadTemplate

Mudline

30 x 1.5" Conductor (1st ST2 Connector)

(Bottom of Model)

Tension Ring

Upper riser monitoring

strain, rotation, tension

Mid-riser monitoring

lateral motions

Lower riser monitoring

strain, lateral motion

Vessel monitoring

overshot strain, lateral

motion, wave, current

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Conclusions

Conventional jackup conductor and riser arrangements do not scale well to ‘deep’ water (>>80m)

Large dynamic jackup motionsHigh dynamic loading on riserLimited flexibility in riser components

Jackups in depths of ~130m with 7000psi pressures are possible through

Improved analysis methodologiesOperational proceduresDesign changes to riser and vesselIntegrity management of installed riser

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Questions?E: Alex.Rimmer@2hoffshore.comT: +44 1483 774925

Questions?

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