turret mooring design - some challenges and solutions

8/10/2019 Turret Mooring Design - Some Challenges and Solutions

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Innovative Technologies, Creative Solutions

Turret Mooring Design Some Challenges and Solutions

FPSO Forum 2004 NUS, Singapore

Arun Duggal

FMC SOFEC Floating Systems

www.sofec.com31 March 2004


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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


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Typical Permanent Internal Turret System

Bearing (only upper in this case)

Turret Shaft / Riser Guide Tubes

Chain Table (Hawse Pipes/Chain Supports)

6 Anchor Legs + 34 Risers

Barracuda FPSO: Campos Basin

834m, 34 RisersSwivel Stack (Product/Lift/Controls)

Anchor Leg + Riser Pull-In Equipment

Manifolds + Pig Launching/Receiving


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Design Considerations

Mooring System Anchor Legs Anchors Risers Thrusters & DP

Control

Environment Water Depth Waves Wind Current

Vessel Particulars Storage / Tonnage Topsides Layout Vessel Motions

Turret Design Configuration Size Location Loads

Turret Mooring ofProduction Vessels

Fluid-Transfer Requirements Well Heads

Subsea Manifolding Risers Turret Manifolding Swivels Offloading Pigging


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Some Current Turret Mooring Challenges

More Complex Turret Systems Large number of risers Increased requirements for turret mounted equipment High pressures

Riser Systems for very Shallow or Deep Water Project Schedule

Short, fast-track schedules Project Design Basis not well defined Interfaces and Communication

Installation in Deepwater Installation engineering, equipment, costs


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Example 1: Fast-Track FPSO for Shallow Water

Su Tu Den FPSO, Vietnam MODEC, Inc + FMC SOFEC + ConocoPhillips

Newbuild FPSO (80,000 bbl oil/day)

Schedule: Contact to First Oil 19 months Turret Delivery Schedule 12 months

Shallow Water (48m water depth)

Harsh Environment (100-yr wave of 8.1m Hs) Large Number of Risers (12)


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Project Milestones 2002 Mar. Contract Award (LOI)(2002/03/21) 2002 Apr. Order Long Lead Items bearing, forgings, process 2002 Jun. Mooring Design Complete 2002 Aug. Turret Fabrication Begins (MSE) 2002 Oct. Hull Fabrication Begins (Samsung) 2002 Nov. Preliminary Riser Design Complete 2002 Dec. Topside Fabrication Begins 2003 Mar. Drydock Block Assembly Begins 2003 Apr. Start Topside Module and Turret Installation 2003 May Launching 2003 Jul. Start Shipyard Commissioning 2003 Sep. Tow Out 2003 Oct. Offshore Installation 2003 Oct. 1st Oil (2003/10/29)


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STD Turret Mooring Design & Fabrication

Use Standard Components & Design SOFEC Large External Turret Design

Bearing Capacity exceeds anticipated Design Loads Allows order of main components before final loads

derived Design Riser Configuration Flexibility in Chain

Table Design/Fabrication

Clearly Define all Structural and Fluid transferInterfaces at Turret Support Structure

Parallel Design and Fabrication Effort

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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Application

FPSO weathervaning SPM Large field (>100,000 bbld) 50 to 100+ risers Deep to ultra deep water Worldwide

Weathervaning advantages Mooring tensions Tandem offloading

Simplified turret structure Allows for simple interface with vessel

Robust bearing system

Large Decks for Flowline Manifolding,and other Equipment Efficient Mooring & Riser Installation

Equipment

Example 2: Very Large Turret


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ChainTable

I-Tubes

Support Columns

Chain Supports

MainDeck

TorqueArm

Vertical Bearing

Radial

Bearing

Swivel Stack &Torque Tube

Piping /Manifolding

Riser Hang-Off

Pull-InDeck

Anchor Legs Risers & Bend Stiffeners

VLT: Deep Water, Large Capacity Internal Turret


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VLT Chain Table 3x3 mooring provides 3

riser corridors Riser quantity defines

chain table (and turret)diameter

60 risers - 22 m dia 90 risers - 31 m dia 120 risers - 40 m dia

2 riser rows maximum No shadowing to allow

inner row installation andreplacement


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Conclusions

Turret Moored FPSOs are a Very Mature Technology Design for Load Transfer is typically not an issue Current challenges mostly associated with Fluid Transfer

Large Number of Risers

High Pressure

ManifoldingSubsea Intervention & Control

Project Parameters also Impact Turret Mooring Design Schedule

Fast-track: 18 22 months

Complex systems require more commissioning time Communication & Interfaces among various contractors / client Knowledge of others scope of work, issues, etc.

turret mooring design - some challenges and solutions

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