KULIAH UMUM Sekretariat IA ITB, Jakarta – 20 November 2010
INTRODUCTION TO FLOATING STRUCTURE
Indratmo Jaring Prasojo (
[email protected])
AGENDA 1.Main Ideas 2.Basic Concepts 3.Type and Function of Floaters 4.Semi-Submersible 5.Tension Leg Platform 6.Spar 7.FPSO 8.Conclusion
Main Ideas Limitations on Fixed Structure (cont’d)
Fixed platforms are economically feasible for installation in water depths up to about 1,700 ft (400 m) More than 400 meter?
COMPLIANT TOWER typically used in water depths ranging from 1,500 to 3,000 feet (400 to 550 m)
Main Ideas Compliant Towers
Main Idea Limitations on Fixed Structure (cont’d) • Tall structures result in resonant wave response (structural natural period close to wave period) • Increase in base shear and overturning moments (stronger structure increases costs) • Limitation on transportation barges • Limitation on lifting barges capabilities
Basic Concepts 1. Buoyancy must equal weight plus any external vertical forces Buoyancy = weight + vertical loads
Buoyancy < weight + vertical loads
Vertical loads include:
Basic Concepts Archimedes Principle Where: B = Buoyancy Force ρ = fluid density Vdisp = Displaced volume (volume terendam) g = gravitational acceleration
Basic Concepts 2. The weight shall be positioned such that the hull will not tip over T T y L p P h o o n S e a s t the TLP had Due to Hurricane Rita, the sea star TLP lost its tether. Without tether unbalanced weight distribution which made it tip over a r Hurricane Rita, September 2005
Basic Concepts 3. There should be enough Reserve Buoyancy to maintain balance and stability even with tanks flooded
Basic Concepts Study Cases
P-36 Semi-submersible Roncador Field off the coast of Brazil
Thunderhorse Semi-submersible US$ 5 Billion, 150 miles offshore of Texas, GoM
June 2005 HURRICANE DENNIS
March 2001 EXPLOSION
There was deck hull acting as reserve buoyancy in Thuderhorse which saved it. No reserve bouyancy available in P-36.
Basic Concepts 4. The platform should stably support the deck above the highest wave crest
Basic Concepts SHIP NOMENCLATURE
Basic Concepts SHIP GEOMETRY Moving forward
Basic Concepts STABILITY Stability is the ability of a system to return to its undisturbed position after an external force is removed (KrishThiagarajan – Handbook of Offshore Str)
Static Due to steady wind force
Stability Dynamic When a sudden gust blows along with steady wind
Basic Concepts STABILITY 1. Transverse Stability
Positively Stable
Negatively Stable = Unstable
Basic Concepts STABILITY Metacenter Point (M)
K = Keel Point G = Centre of Gravity B = Centre of Buoyancy M = Intersection between B and centerline GM = Distance between G and M → Metacenter Height
STABLE, GM > 0
Basic Concepts STABILITY Metacenter Height (GM)
GM = KB + BM - KG
Second moment of waterplane area about x-axis Submerged volume
Basic Concepts STABILITY 2. Longitudinal Stability
GMl = KB + BMl - KG
Basic Concepts STABILITY DYNAMIC Stability The dynamic stability criteria for a ship or FPSO are set based on the stability requirement to withstand a sudden environmental change, e.g. a gust of wind. Vessels that are intact are required under the ABS certification to be able to withstand a 100-knot (51 m/s) wind in a storm impact condition. In a damaged condition, the vessel should have sufficient stability to withstand a 50-knot (25.7 m/s) wind.
Type &function of Floaters FUNCTIONS 1. 2. 3. 4. 5.
Exploratory Drilling: Drillships, semi-submersible, Jack-ups, barges Production and Drilling: Semi-submersibles, Spars, TLs Production and Storage: Ship conversions, Newbuild ship & barges Pipelaying: Barges, semi-submersibles Construction/Derrick Vessels: barges, semi-submersibles
PARAMETERS TO SELECT FLOATER TYPE 1. 2. 3. 4.
Platform drilling or MODU drilling Water Depth Environment Wet or dry tree Function Export by pipeline or tanker
Type &function of Floaters WET & DRY TREES Reservoir drivers
Type &function of Floaters HULL SELECTION CRITERIA
Semi-submersibles HISTORY Submersible
Semi-Submersible Before 1971 Lack of Consistency in design
Pentagone Rig
Sedco 135 Rig
Semi-submersibles HISTORY Submersible
Semi-Submersible Between 1971-1980 Most Common Rigs today Twin hulls High mobility Standardization MODU Classification rules
Aker H3 Production Semi-submersible
Semi-submersibles HISTORY Submersible
Semi-Submersible Between 1981-1984 Twin Hulls Well designed bracings Hull type superstructure
Odyssey
Semi-submersibles HISTORY Submersible
Semi-Submersible Between 1984-1998 Larger Deepwater Harsh Environment
Marine 700
Semi-submersibles HISTORY Submersible
Semi-Submersible Between 1999 - 2009 Ultra Deepwater
Transocean
Deepwater Nautilus
Semi-submersibles HISTORY Submersible
Semi-Submersible Between 2010 - ….. Ultra Deepwater
Petro Rig 1 – Sembcorp Marine
Semi-submersibles FUNCTIONS Production, Drilling &Workover
CAPABILITIES Waterdepth: 80 – 3,000 m Process capacity is up to 180,000 bpd
CURRENT PRESENCE North Sea, Brazil, Asia, Gulf of Mexico (GoM)
Semi-submersibles
Semi-submersibles
Semi-submersibles DESIGN PRINCIPLES 1 Consist of deck, multiple columns, pontoon and space frame bracings 2 Centre of gravity (cog) is above the centre of buoyancy (cob) SPAR stability is achieved by positioning cog* below cob* TLP stability is derived from the tendons 3 Main Functions of Semis: a. To stably support a payload above the highest waves b. To minimally respond to waves Number, size, spacing of stability columns Height of the deck )* cog = centre of gravity; cob = centre of buoyancy
Tension Leg Platform (TLP) TERMINOLOGY
APIRP2T
Tension Leg Platform (TLP) RESPONSE CHARACTERISTICS More Rigid
More Compliant
(More Fixed)
TLP (heave, roll, pitch)
Energy
Spar Semi
0
5
10
15
Wave Period (s)
20
25
30
Tension Leg Platform (TLP) FUNCTIONS
Production, Drilling, Workover& Wellhead Support
CAPABILITIES
Waterdepth: 150 – 1,500 m Process capacity is up to 220,000 bpd
CURRENT PRESENCE
North Sea, West Africa, Gulf of Mexico (GoM)
Tension Leg Platform (TLP) FLOATERS INSTALLED & UNDER CONSTRUCTION Current TLP Depth Limit
45000 40000
Thunder Horse
Topsides Weight, tons
35000
Ursa
Auger
At lant is
Spars 30000
Holst ein
Semis Mini-TLPs
25000
Large Topside Wet Tree Market
Diana
Mars Ram,/ Powell
TLPs
Na Kika MadDog
20000 Genesis
Kizomba (E-TLP)
15000 Front runner
10000
Gunnison
Nept une West Senu
Horn Mt n. Devils Tower
Marco Polo
Marlin Jolliet
Magnolia
Medusa
5000
Red Hawk
Boomvang/ Nansen Prince
Typhoon
Mat t erhorn Allegheny
Morpet h
0 0
1000
2000
Minimal Facilities Market
3000
4000
Water Depth, ft.
5000
6000
7000
Tension Leg Platform (TLP) TLP DEVELOPMENT (since 1983 = 25 TLPs)
Tension Leg Platform (TLP) TYPES OF TLP 1. CONVENTIONAL
Shell’s Brutus TLP during topsides installation in Corpus Christi, TX, in 2001.
Shell’s Ram Powell TLP is located in 3,214ft of water at Viosca Knoll, block 956, in the Gulf Of Mexico
Tension Leg Platform (TLP) TYPES OF TLP 2. E-TLP •
• • • ABB
Reason for leg extensions – Wider tendon base for greater pitch stiffness (stability) – Smaller spacing of deck supports for more efficient structure – Lower rotational inertia for hull and deck for lower pitch natural period Approximately 40 percent lighter hull than for a comparable, conventional TLP. A large moonpool can accommodate conventional top tension risers. De-coupling of tendon porch separation distance from the topsides deck design produces maximum design flexibility.
Tension Leg Platform (TLP) TYPES OF TLP 3. MODEC MOSES
•
Key points of the TLP design – minimal impact of wave loading – minimum tendon tension to obtain required platform response. – Low-cost tendon design with standard mill run tubulars, threaded casing couplings and low cost top and bottom tendon connectors. – A well and riser system with standard 9 5/8" casing – short stroke riser tensioner. – a lighter deck structure. – Well drilling or workover capability utilizing leased compact, lightweight, platform rigs. – A flexible installation method using SSDV, Multi-Service Vessels, or derrick barge
Tension Leg Platform (TLP) TYPES OF TLP 4. MINI TLP
SEA STAR
•
Monocolumn Hull – Stiffened plate construction – Standard mild-grade,thin-plate steels – Fabricated in small modules – Assembled as complete unit at quayside – No ballasting required during operation – Compartmentalized hull prevents flooding – Hull can be lengthened to increase payload – All compartments are accessible for inspection
•
Tendons – Tubular steel elements – Multiple,mechanically coupled sections – Design fatigue life typically exceeds 1000years, (API-requirement 200 years) – Tendon pairs have redundancy – Tendons are neutrally buoyant to minimize payload and hull displacement – Fairings are installed on the tendons to preventvortex-induced vibrations.
Tension Leg Platform (TLP) DESIGN DRIVERS o o o o o
Heave and pitch natural periods less than 4 seconds. Minimizing bending loads on TLP deck structure Minimizing (pitch-induced) tether tensions Acceptable offset and setdown Installation stability
Tension Leg Platform (TLP) PURPOSE OF TETHERS • Stationkeeping – vessel offset kept to prescribed limits (~5% of WD) • Vertical stiffness – reduce heave, pitch and roll motions to accommodate rigid vertical risers with dry trees • Lateral stiffness – minimize surge, sway and yaw slow drift motions
Tension Leg Platform (TLP) INSTALLATION • Conventional TLPs are stable with deck load and may be towed into position. • Mini-TLPs and ETLP may not be stable and require derrick barge or external temporary buoyancy for installation • This factor should be considered in design
SPAR FUNCTIONS
Production, Drilling, Workover, Wellhead Support & Oil Storage
CAPABILITIES
Waterdepth: 150 – 1,500 m Process capacity is up to 220,000 bpd
CURRENT PRESENCE Malaysia, Gulf of Mexico (GoM)
SPAR
Basic Parts:
SPAR HARD TANK STRUCTURAL ARRANGEMENT
SPAR
Progression of SPAR
SPAR TRANSPORTATION & INSTALLATION
SPAR TRANSPORTATION & INSTALLATION
Truss Spar Wet Tow
SPAR TRANSPORTATION & INSTALLATION
Truss Spar Upending
SPAR TRANSPORTATION & INSTALLATION
Truss Spar Upended
SPAR TRANSPORTATION & INSTALLATION
Add solid ballast
SPAR TRANSPORTATION & INSTALLATION
Topside Lifting
SPAR TRANSPORTATION & INSTALLATION
Topside Floatover Installation
FPSO FUNCTIONS
Production, Storage & Offloading
CAPABILITIES
Waterdepth: 30 – 3,000 m Process capacity is up to 200,000 bpd Storage is up to 2 mmbbl
CURRENT PRESENCE
North Sea, North Atlantic, Canada, Mediterranian, Africa, Brazil, Asia
FPSO TYPICAL CONFIGURATION OF NEW-BUILD FPSO
Typical Tanker Based FPSO
FPSO FEATURES & ATTRACTIONS
FPSO TYPICAL SIZE OF FPSO
FPSO TYPICAL SIZE OF FPSO
FPSO
FPSO MOORING SYSTEM 1. Turret Moored
INTERNAL EXTERNAL 2. Spread Mooring
FPSO MOORING SYSTEM 1. Turret Moored •All mooring lines are attached to turret • All risers routed through turret • Suitable for harsh environment • Disconnection possible • Current presence: North Sea, North Atlantic
FPSO MOORING SYSTEM 2. Spread Moorings • Mooring Lines are routed to optimum position on vessel • Risers are routed alongside of vessel • Suitable for moderate environment • Current presence: Brazil, West Africa
CONCLUSION Existing Function of Floaters
CONCLUSION Rules of Thumb for Configuration Sizing
CONCLUSION Rules of Thumb for Configuration Sizing
REFERENCES 1 Lecture Slides on Design of Floating Structure course – National University of Singapore • Dr. John Halkyard • Prof. KrishThiagarajan • Guest Lecture from SBM Offshore 2 Handbook of Offshore Engineering • Dr. John Halkyard • Prof. KrishThiagarajan 3 Handbook of Offshore Engineering 4 www.offshore-technology.com 5 Other websites
