Transcript Field Layout with Tension Leg Risers

Turret Mooring Design –
Some Challenges and Solutions
FPSO Forum 2004
NUS, Singapore
Arun Duggal
FMC SOFEC Floating Systems
www.sofec.com
31 March 2004
Innovative Technologies, Creative Solutions
FPSOs are a Mature & Versatile FPS Technology
• Over 100 units in operation worldwide
• FPSO total > than all other FPS combined
• Water depth range 20 m to > 1,400 meters
• 1 to 100+ risers
• 10,000 bbl – 250,000 bbls/day
• Up to 2,000,000+ bbls storage
• Benign (West Africa) to Extreme Environments (North
Atlantic)
• Various flavors:
• Turret-moored
• Spread-moored
• Yoke-moored
• Hawser-moored
Innovative Technologies, Creative Solutions
Typical Permanent Internal Turret System
Barracuda FPSO: Campos Basin
834m, 34 Risers
Swivel Stack (Product/Lift/Controls)
Manifolds + Pig Launching/Receiving
Anchor Leg + Riser Pull-In Equipment
Bearing (only upper in this case)
Turret Shaft / Riser Guide Tubes
Chain Table (Hawse Pipes/Chain Supports)
6 Anchor Legs + 34 Risers
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Design Considerations
Vessel Particulars
Environment
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Water Depth
Waves
Wind
Current
Turret Design
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Configuration
Size
Location
Loads
Turret Mooring of
Production Vessels
Fluid-Transfer Requirements
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Innovative Technologies, Creative Solutions
Well Heads
Subsea Manifolding
Risers
Turret Manifolding
Swivels
Offloading
Pigging
• Storage / Tonnage
• Topsides Layout
• Vessel Motions
Mooring System
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Anchor Legs
Anchors
Risers
Thrusters & DP
Control
Some Current Turret Mooring Challenges
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More Complex Turret Systems
– Large number of risers
– Increased requirements for turret mounted equipment
– High pressures
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Riser Systems for very Shallow or Deep Water
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Project Schedule
– Short, fast-track schedules
– Project Design Basis not well defined
– Interfaces and Communication
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Installation in Deepwater
– Installation engineering, equipment, costs
Innovative Technologies, Creative Solutions
Example 1: Fast-Track FPSO for Shallow Water
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Su Tu Den FPSO, Vietnam
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MODEC, Inc + FMC SOFEC + ConocoPhillips
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Newbuild FPSO (80,000 bbl oil/day)
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Schedule: Contact to First Oil – 19 months
– Turret Delivery Schedule – 12 months
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Shallow Water (48m water depth)
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Harsh Environment (100-yr wave of 8.1m Hs)
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Large Number of Risers (12)
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Project Milestones
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2002 Mar.
Contract Award (LOI)(2002/03/21)
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2002 Apr.
Order Long Lead Items – bearing, forgings, process
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2002 Jun.
Mooring Design Complete
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2002 Aug.
Turret Fabrication Begins (MSE)
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2002 Oct.
Hull Fabrication Begins (Samsung)
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2002 Nov.
Preliminary Riser Design Complete
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2002 Dec.
Topside Fabrication Begins
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2003 Mar.
Drydock – Block Assembly Begins
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2003 Apr.
Start Topside Module and Turret Installation
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2003 May
Launching
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2003 Jul.
Start Shipyard Commissioning
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2003 Sep.
Tow Out
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2003 Oct.
Offshore Installation
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2003 Oct.
1st Oil (2003/10/29)
Innovative Technologies, Creative Solutions
STD Turret Mooring Design & Fabrication
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Use Standard Components & Design
– SOFEC Large External Turret Design
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Bearing Capacity exceeds anticipated Design Loads
– Allows order of main components before final loads
derived
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Design Riser Configuration Flexibility in Chain Table
Design/Fabrication
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Clearly Define all Structural and Fluid transfer
Interfaces at Turret Support Structure
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Parallel Design and Fabrication Effort
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Easy / Quick Integration with Vessel
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Riser & Mooring Design in Shallow Water
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Mooring and Riser Design 2
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Integration of Turret & Vessel
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First Oil: November 2003
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Example 2: Very Large Turret
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Application
– FPSO weathervaning SPM
– Large field (>100,000 bbld)
– 50 to 100+ risers
– Deep to ultra deep water
– Worldwide
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Weathervaning advantages
– Mooring tensions
– Tandem offloading
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Simplified turret structure
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Allows for simple interface with vessel
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Robust bearing system
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Large Decks for Flowline Manifolding,
and other Equipment
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Efficient Mooring & Riser Installation
Equipment
Innovative Technologies, Creative Solutions
VLT: Deep Water, Large Capacity Internal Turret
Torque
Arm
Pull-In
Deck
Swivel Stack &
Torque Tube
Piping /
Manifolding
Radial
Bearing
Main
Deck
I-Tubes
Vertical Bearing
Riser Hang-Off
Support Columns
Chain
Table
Innovative Technologies, Creative Solutions
Anchor Legs
Chain Supports
Risers & Bend Stiffeners
VLT Chain Table
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3x3 mooring provides 3
riser corridors
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Riser quantity defines
chain table (and turret)
diameter
– 60 risers - 22 m dia
– 90 risers - 31 m dia
– 120 risers - 40 m dia
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2 riser rows maximum
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No shadowing to allow
inner row installation and
replacement
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VLT Main Deck
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Supports all loads, including:
– Riser hang-off loads
– Mooring loads through chain
table and support columns
– Turret self weight
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Depth-to-diameter ratio is a key
design parameter
– Flexibility to move with vessel
– Strength to support risers,
mooring and turret weight loads
– 2.5 m depth / 32 m diameter for
a 90 riser VLT
Innovative Technologies, Creative Solutions
Conclusions
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Turret Moored FPSOs are a Very Mature Technology
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Design for Load Transfer is typically not an issue
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Current challenges mostly associated with Fluid Transfer
Large Number of Risers
High Pressure
Manifolding
Subsea Intervention & Control
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Project Parameters also Impact Turret Mooring Design
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Schedule
Fast-track: 18 – 22 months
Complex systems require more commissioning time
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Communication & Interfaces – among various contractors / client
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Knowledge of others scope of work, issues, etc.
Innovative Technologies, Creative Solutions