Engineering Aspects of Engineering Aspects of Offshore HeavyOffshore Heavy--Lift & Lift &

TransportationTransportation

Presentation to Aberdeen Presentation to Aberdeen IStructEIStructE2424thth February 2005February 2005

Jon Jon DunstanDunstan

IntroductionIntroduction

Just Just before before the final positioning at sea, production the final positioning at sea, production platforms for the exploration of oil and natural gas are platforms for the exploration of oil and natural gas are now now assembled almost to the point of completion. assembled almost to the point of completion. This This approachapproach requires the ability to move and lift large and requires the ability to move and lift large and heavy items at the yardheavy items at the yard as well as transporting them as well as transporting them by sea to their final location and installing them on the by sea to their final location and installing them on the seabed.seabed.

Industry has evolved to provide the tools and methodsIndustry has evolved to provide the tools and methodsto facilitate this high level of completion. Work offshoreto facilitate this high level of completion. Work offshorecan cost 10 x cost of onshore.can cost 10 x cost of onshore.

The Driving factorsThe Driving factorsPlatform Designer & FabricatorPlatform Designer & Fabricator--Minimise steel and equipment required for transport/installationMinimise steel and equipment required for transport/installation phases phases --Maximise onshore hookMaximise onshore hook--up and completionsup and completions

Transport & Installation (T&I) ContractorTransport & Installation (T&I) Contractor--Simplify lifts as far as possibleSimplify lifts as far as possible--maximise access and flexibility for marine operationsmaximise access and flexibility for marine operations--Minimise weather sensitivityMinimise weather sensitivity--Minimise danger to marine equipmentMinimise danger to marine equipment--maximise onshore preparationmaximise onshore preparation

OperatorOperator--Perform safe and quick installation, minimise riskPerform safe and quick installation, minimise risk--Minimise time between installation to first oilMinimise time between installation to first oil--Maximise efficiency/costMaximise efficiency/cost

The Basic stepsThe Basic steps1.Design & Fabricate Structure Onshore

2.Hook-up & Commission as a far as possible

3.Transfer (Load-out) structure onto barge/vessel for ocean tow

4.Tow to construction location in the field

5. Remove structures from barge and position in field

6. Secure structure in position

7. Offshore Hook-Up, testing & Commissioning

8. Operation

9. Shutdown, decommissioning and removal

STEPS 1 TO 3 – DESIGNER/FABRICATOR

STEPS 4 TO 6 – TRANSPORT & INSTALLATION (T&I) CONTRACTOR

STEPS 7 TO 8 – PLATFORM OPERATOR

Offshore StructuresOffshore StructuresPushing the limitsPushing the limits

1000'

3000'

5000'

2000'

4000'

6000'

FIXEDPLATFORM

FPSO

COMPLIANTTOWER

FPS

TLP

SUBSEACOPLETIONTh e d e e p e s t o f t h e d e e p

SPAR

1000 ft

4000 ft

3000 ft

2000 ft

5000 ft

6000 ft

History of Construction MethodsHistory of Construction Methods

Jackets – Launched/towed

Topsides – Multiple Module Assembly (MSF & stacked modules, offshore hook-up)

The North Sea Boom The North Sea Boom

A need for increased capacity and specialist tools. A step chanA need for increased capacity and specialist tools. A step change in design.ge in design.The birth of the semiThe birth of the semi--submersible crane vessel (SSCV) submersible crane vessel (SSCV) -- 6,3506,350 mtmt lift capacitylift capacity

14,000 tonnes14,000 tonnesM7000M700019871987

14,000 tonnes14,000 tonnesThialfThialf (ex. DB102) / (ex. DB102) / S7000S7000

20002000

12,000 tonnes12,000 tonnesDB102DB10219891989

8,165 tonnes8,165 tonnesHermodHermod19851985

6,350 tonnes6,350 tonnesBalderBalder19841984

2,722 tonnes2,722 tonnesOdinOdin19761976

1,800 tonnes1,800 tonnesThorThor19741974

1,135 tonnes1,135 tonnesChampionChampion19721972

725 tonnes725 tonnesChallengerChallenger19691969

250 tonnes250 tonnesHerculesHercules19601960

Lift CapacityLift CapacityVesselVesselYearYear

Design RevolutionDesign Revolution--One piece topsides (Integrated Deck) revolutionisesOne piece topsides (Integrated Deck) revolutionisesoffshore installation and hookoffshore installation and hook--up. Lifted jackets avoidup. Lifted jackets avoid

need to design jackets for launch need to design jackets for launch

--Modules can be mechanically complete & commissionedModules can be mechanically complete & commissioned•• 2 lifts only (1 x jacket, 1 x deck)2 lifts only (1 x jacket, 1 x deck)

DESIGNING & PREPARING FOR PLATFORM TRANSPORT & INSTALLATION

PreparationPreparation•• OPERATIONALOPERATIONAL

•• Structure weighingStructure weighing•• Dimensional Control Dimensional Control

ChecksChecks•• Preinstall Lift RiggingPreinstall Lift Rigging•• Barge/vessel ArrivalBarge/vessel Arrival•• Barge Vessel MooringBarge Vessel Mooring•• Barge outfitting of Barge outfitting of

grillagegrillage•• Installation of Installation of linkspanlinkspan•• Transfer of Structure to Transfer of Structure to

quayside

•• DESIGNDESIGN

•• All temporary phases (All temporary phases (loadoutloadout, , transport, lift, ontransport, lift, on--bottom bottom stability, launch) assessed for stability, launch) assessed for strength strength

•• Local checks at interface pointsLocal checks at interface points•• Design of Grillage & Design of Grillage &

SeafasteningSeafastening•• Lift Rigging DesignLift Rigging Design•• Dynamic lift simulationsDynamic lift simulations•• Launch AnalysisLaunch Analysis•• Pile Driveability checksPile Driveability checksquayside

Preparations Before Preparations Before loadoutloadout

Preconnection of Lift Slings to padeyes/padears/trunnions

Rigging Laydown & securing

LoadoutLoadout

•• Transfer of structure from Transfer of structure from fabrication yard onto fabrication yard onto barge/vesselbarge/vessel

•• Method of Method of loadoutloadout--LiftedLifted--SkiddedSkidded--Trailers (SPMT)Trailers (SPMT)

•• Ballasting of barge to maintain Ballasting of barge to maintain level platform between level platform between quayside and barge deckquayside and barge deck

Assessment of Assessment of Loadout Loadout ConditionCondition•• Reactions from trailers (onto structure)Reactions from trailers (onto structure)•• Calculation of No. of trailers required (Calculation of No. of trailers required (typtyp. 30mt/axle). 30mt/axle)•• Skidshoe Skidshoe design/reactionsdesign/reactions-- required winch/strand jack required winch/strand jack

capacity/design of anchor pointscapacity/design of anchor points•• Influence of accelerationInfluence of acceleration•• Overall StabilityOverall Stability•• Physical clearancesPhysical clearances•• Link span end reactions check on barge & quayLink span end reactions check on barge & quay•• Link span strengthLink span strength•• UDL loads on quay, UDL loads on quay, linkspan linkspan and barge from trailersand barge from trailers•• (standard barge capacity, 10(standard barge capacity, 10--15mt/m15mt/m22))

SetSet--Down on BargeDown on BargeIntroductionIntroduction

•• Gradual Load Transfer Gradual Load Transfer onto Barge ‘Grillage’ onto Barge ‘Grillage’

•• Packing/shimming for Packing/shimming for even load distribution (up even load distribution (up to 48 support points)to 48 support points)

•• Acceptance by structure Acceptance by structure designerdesigner

•• Barge ballasted to ‘mimic Barge ballasted to ‘mimic tow’tow’

Design of Grillage & Design of Grillage & Seafastening Seafastening (1)(1)•• LoadsLoads--StaticStatic--DynamicDynamic--Lift/launchLift/launch--Deck SetDeck Set--down /matingdown /mating--FatigueFatigue--Wave slamWave slam--Details for simple removal Details for simple removal

& cutting offshore (gusset & cutting offshore (gusset plates)plates)

Seafastening braces

Grillage beams

Loadout frame

Design of Grillage &Design of Grillage &SeafasteningSeafastening (2)(2)

Methods of Analysis of Transportation Loads

1. Full Dynamic Analysis (irregular seastates, wave spectrum, consideration of phases, wave approach direction,

natural periods, roll damping)

-SACS

-MOSES

2. Noble Denton ’20 & 10’ approach – Simple Harmonic Motion

Model

-20 degrees roll in 10 seconds

-Simple spreadsheet, quasi-static assessment

-Conservative (Pitch (B or S) +/- heave, Roll ( P or S) +/- heave)

Design of Grillage &Design of Grillage &SeafasteningSeafastening (3)(3)

Noble Denton ’20 & 10’ Noble Denton ’20 & 10’ –– calculation of forces at calculation of forces at cargo cargo CoG CoG for Rollfor Roll

Design of Grillage &Design of Grillage &SeafasteningSeafastening (3)(3)Seafastening Seafastening DesignDesign

•• Dynamic loads only (Takes Dynamic loads only (Takes Fh Fh only)only)•• Generally taken axially in braces or in bearing via ‘shear stopsGenerally taken axially in braces or in bearing via ‘shear stops’’•• Any resulting couple taken as vertical loads through grillageAny resulting couple taken as vertical loads through grillage•• Allow 33% over normal allowable API/AISC stressesAllow 33% over normal allowable API/AISC stresses•• Gusset connections for easy removal (single plane strength only)Gusset connections for easy removal (single plane strength only)•• Possibility of roll ‘relief’ or roll ‘addition’Possibility of roll ‘relief’ or roll ‘addition’

Barge/Vessel Strength Barge/Vessel Strength

•• Support structure Support structure (grillage) to transfer (grillage) to transfer static loads and static loads and proportion of dynamic proportion of dynamic loads into barge/vessel loads into barge/vessel superstructuresuperstructure

•• Identification of barge Identification of barge transverse & longitudinal transverse & longitudinal frame capacitiesframe capacities

•• Grillages span Grillages span hardpointshardpoints•• Hog/Sag conditions for Hog/Sag conditions for

long structures (barge long structures (barge bending ‘encouraged’)bending ‘encouraged’)

Transport to FieldTransport to Field

Considerations:

-Distance

-Duration

-Cost

-risk

-Vessel cost &

availability

Self Propelled Vessel

Tug & Barge

Jackets (Lift)Jackets (Lift)

Single Crane Lift Tandem (Dual Crane) Lift

Upending sequenceUpending sequence

Jackets (Launch)Jackets (Launch)

Barge Ballasted to stern Launch over stern Hook-Assisted Upend

Ballast Control Station

PilingPiling

hammer

‘Through-Leg’ Pile driving Piling sequence Piling Hammers

I L T

Pile lift off from barge & Upend (190m each, 820mt)

Platform & jacket Platform & jacket preparationspreparations

Bumper

Guide•• Bumpers/guidesBumpers/guides•• Stabbing conesStabbing cones•• Jacket levellingJacket levelling•• Leg cutLeg cut--offsoffs

Lift (Decks & Modules)Lift (Decks & Modules)

SINGLE CRANE LIFT DUAL CRANE DECK LIFT

Designing for LiftDesigning for Lift-Requirement for Spreader Bars /frames

-Lift Point design

-Sling selection (sling/grommet/doubled)

-Shackle selection

-Bending Losses

-Sling extension

-Module tilt /CoG position

-Rigging removals (hydraulic shackles)

FloatoversFloatovers

-Well suited to benign environments (SE Asia /Middle East/Caspian/W Africa)

-Jacket installed by launch

-Deck towed out on barge or HLV

-Legs overhang barge

-Barge floated between jacket legs

-Barge ballasted to set-down deck

-No crane vessel required

-Builds on old ‘GBS’ technology

The FutureThe FutureNORTH SEA

-Few new structures

-More subsea and upgrade work

-Decommissioning – TFE Frigg field

-reverse installation

-Weather limits

-piecemeal removal

-newbuild removal vessels

REST OF WORLD

-Move to deeper water requires floating facilities

-Less construction work for ‘jacket and deck’ construction

What can go wrong?What can go wrong?

ENDEND

WITH THANKS TO HEEREMA MARINE CONTRACTORSWITH THANKS TO HEEREMA MARINE CONTRACTORS