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?
©2015 NOV | Proprietary and confidential. Presentation Name - 00/00/00 | 32
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