Innovative Riser Configurations for Ultra Shallow Water Emad Libis, NOV Flexibles Claus Dencker Christensen, NOV Flexibles February 26, 2015
Innovative Riser Configurations for
Ultra Shallow Water
Emad Libis, NOV FlexiblesClaus Dencker Christensen, NOV Flexibles
February 26, 2015
Agenda
�Intro�Motivation�Typical Challenges in Ultra Shallow Water�A Robust Solution�Validation�Further Enhancements�Summary and Conclusion
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
©2014 NOV | Proprietary and confidential. 3
FLEXIBLE RISERS, INTRO
� Intro� Motivation� Typical Challenges in Ultra Shallow Water� A Robust Solution� Validation� Further Enhancements� Summary and Conclusion
Intro, Biography
Emad Libis� MSc Structural Engineering 2012� National Oilwell Varco 2012 - Date
Pipe System Design EngineerExchange member, Specialist & Sales Unit
Main engineer, Asia-Pacific, System Design
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Claus Dencker Christensen� MSc, PhD Structural and
Hydraulic Engineering 1996� Offshore Technology, DHI 1996 - 2006� National Oilwell Varco 2006 - Date
Technical Authority, System DesignPrincipal Engineer, System DesignLeads NOV Specialist & Sales Engineering Unit
Involved in all NOV Asia-Pacific projects since 2007
Intro, Flexible Risers
Pipe Designs:
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Basic Configurations:
©2014 NOV | Proprietary and confidential. 6
MOTIVATION
� Intro� Motivation� Typical Challenges in Ultra Shallow Water� A Robust Solution� Validation� Further Enhancements� Summary and Conclusion
Motivation� Most easy accessible oil/gas reserves exhausted� Trunklines expensive for new fields� FPSO becomes economically preferable� Un-bonded flexible risers absorb FPSO motion� Most challenging new development:
� Extreme water depth (>1000 m)� Rough environment ultra shallow water (<<100 m)
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Motivation, Typical Riser SystemsFlexible riser systems, examples:
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Fixed-S ->Ichthys->
D=280m
TGT->
D=43m
Riser Turret Column -> Bal naves ->
D=79m
Okha->
D=79m
Lazy-S ->
Ichthys->
D=280m
Troll B,
Åsgaard B->
D=350m
Li vorno->
D=112m
Western Is l es->
D=160m
KMZ *4->
D=90m
Dai Hung->
D=111m
Alba->
D=140m
Gryphon->
D=112m
Ettri ck->
D=111m
Maari->
D=104m
Pierce->
D=85m D1 Fiel d->
D=91m
PM-3->
D=62m
Su Tu Vang->
D=54m
Orki d Pakma->
D=58m
Curl ew->
D=91m
Steep Wave ->Hadera->
D=73m
Dumbarton->
D=120m
Martin Li nge->
D=118m
Gryphon->
D=112m
Ettri ck->
D=111mWenchang->
D=125m
Enpi ng->
D=85m
Xi ji ang->
D=91m
Mariner->
D=109m
Rang Dong->
D=60m
Montara->
D=77m
Tethered Wave ->Visund, Njord,
Snorre,etc->
D=330m
Alba->
D=140m
Martin Li nge->
D=118m
Affl eck *1->
D=79m
Brunhi lde *2->
D=85m
Curl ew *3->
D=91m
Lazy Wave -> Kakap->
D=90m
Free Hanging Catenary -> Snorre A->
D=350m
Madura->
D=55m
Wave Height/Water Depth -> [%] 10% 12.50% 18% 25% 33% 50%
*1: Semi-sub, max. 14m offset
*2: Neighbour for Pierce
*3: Heavy Uraduct necessary (Lead), Turret at 80% vessel length, Max. 7" Riser
*4: Steep-S
Sy
ste
m C
om
ple
xit
y/P
rice
Environment Severity
©2014 NOV | Proprietary and confidential. 9
TYPICAL CHALLENGES
� Motivation� Typical Challenges in Ultra Shallow Water� A Robust Solution� Validation� Further Enhancements� Summary and Conclusion
Typical Challenges 1:3
� Vessel “Far” position: Risers stretched
� Vessel “Near” position: Hogbend–Vessel InterferenceSagbend-Seabed InterferenceOverbending Sagbend
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Typical Challenges 2:3� Transverse environment: Interference with mooring or buoyancy
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
� High Downwards Vertical Velocity: Riser snatch over-bending under turret
Typical Challenges 3:3� Large motion of Hogbend/MWA: Overbending touchdown/hog-bend
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
©2014 NOV | Proprietary and confidential. 13
SOLUTION
� Intro� Motivation� Typical Challenges in Ultra Shallow Water� A Robust Solution
Study Case, Step-By-Step1) Basic System Selection (Interference, Touchdown)2) Riser Stiffness Cover (Over-bending Sagbend, BS, Touchdown)3) Restricted-S (Increase Pliancy of Stretched Riser)
� Validation� Further Enhancements� Summary and Conclusion
Solution, Study Case
Example: Most extreme shallow water system known => Wave Height / Depth = 0.42
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Variable Value Water Depth ~43 m Max. Wave Height ~18 m Max. Current Velocity ~2 m/s Number of Risers 7 in one mooring sector Number of Umbilicals 1 in same mooring sector Max. Riser ID ~9” Vessel Type Weathervaning FPSO, Size: Aframax Vessel Draft Range ~7 m -14 m Mooring type Bow-mounted Turret Mooring System 3 x 4 groups mooring legs Max. Vessel Offset (Downstream) ~19 m Max. Vessel Offset (Upstream*) ~5 m
AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Solution, Rejected Systems 1:2Failed solution attempts: Camel Back (Double Wave) , Tethered Wave (Single Wave)
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Start of lifeStart of life
WaterfilledWaterfilled
EmptyEmpty
End of lifeEnd of life
WaterfilledWaterfilled
EmptyEmpty
Solution, Rejected Systems 2:2Decent solution attempt:Lazy-S (MWA Buoy)
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
� Deep water: Risers control (move) MWA Buoy� Shallow water: MWA Buoy controls (moves) risers
MWA Buoy sometimes move opposite FPSO� Therefore: Advantage if MWA Buoy does not move
Solution, Basic System Slide 17
Fixed-S with heavy risers selected:� Helps control interference with vessel� Helps control interference with mooring� Less bending of risers� No buoyancy module interference
AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Maximize pliancy of the configuration:� Minimise distance from structure to the turret centreline� Maximise height of structure
Solution, Restricted -SSlide 18
TurretCL
TurretCL
AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Solution, Restricted -STo gain enough system pliancy:� Place MWA top high in the ”Vessel Exclusion Zone”� Restricted-S is feasible and robust
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Solution, Riser Stiffness CoverControl Overbending of Flexibles:� Use ” Riser Stiffness Cover” to avoid over-bending
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Parameter 9” Riser 9” Riser With RSC MBR Storage [m] 2.66 2.66 Bending Stiffness at 20°C [kNm2] 160 445
Riser Stiffness Cover is an extruded layer typically made from a very robust, durable and stiff polymer. Typically:
HDPE Grade 100
AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Solution, HDPE G100 StatusTested and Proven:
Fatigue Notch Sensitivity
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Materiale Temperatur,°C
23 0 -20 -40
HDPE 28 kJ/m2 24 kJ/m2 25 kJ/m2 26 kJ/m2
MDPE 18 kJ/m2 15 kJ/m2 10 kJ/m2 3 kJ/m2
PA11 87 kJ/m2 100 kJ/m2 5 kJ/m2 5 kJ/m2
Solution, Seabed Guide Structure� Avoid damaging risers by contact� Reduce forces on interfacing structures
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
©2014 NOV | Proprietary and confidential. 23
VALIDATION
� Intro� Motivation� Typical Challenges in Ultra Shallow Water� A Robust Solution� Validation� Further Enhancements� Summary and Conclusion
Validation, Main ResultsMain Results, Examples:
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Validation, ExternalSlide 25
AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
�Physical model tests by client�Full independent dynamic analysis by MCSK, Australia�3rd Party Verification, Bureau Veritas / ABS
©2014 NOV | Proprietary and confidential. 26
FURTHER ENHANCEMENT
� Intro� Motivation� Typical Challenges in Ultra Shallow Water� A Robust Solution� Validation� Further Enhancements� Summary and Conclusion
Further Enhancement� Restricted-S solved this challenge� Even bigger challenges requires new solutions:
Reverse Hang-off :
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Sliding-S:
Further EnhancementSliding-S Animation
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
©2014 NOV | Proprietary and confidential. 29
SUMMERY AND CONCLUSION
� Intro� Motivation� Typical Challenges in Ultra Shallow Water� A Robust Solution� Validation� Further Enhancements� Summary and Conclusion
Summary and ConclusionExamples of challenges in ultra shallow water has been demonstrated.
� A robust Restricted-S solution has been presented� Solution validated with physical model tests� Further enhancements to the solution presented� Riser Stiffness Cover is essential
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AOG • Innovative Riser Configurations for Shallow Water • Claus Dencker Christensen • Emad Libis
Examples: Riser Stiffness Cover
Thank you for your attention.
Questions?
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