Upload
nthong
View
601
Download
0
Embed Size (px)
Citation preview
INTRODUCTION TO
FLOATING STRUCTURE
Sekretariat IA ITB, Jakarta –
20 November 2010
KULIAH UMUM
Indratmo Jaring Prasojo([email protected])
AGENDAAGENDAAGENDAAGENDA
1.Main Ideas
2.Basic Concepts
3.Type and Function of Floaters
4.Semi-Submersible
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)
COMPLIANT TOWERtypically used in water depths ranging from 1,500 to 3,000 feet (400 to 550 m)
More than 400 meter?
Main Ideas
Compliant Towers
Main Idea
• 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)
Limitations on Fixed Structure (cont’d)
(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 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
y
p
h
T
L
P
h
o
o
n
S
e
a
s
t
a
rHurricane Rita, September 2005
Due to Hurricane Rita, the sea star TLP lost its tether. Without tether the TLP had unbalanced weight distribution which made it tip over
Basic Concepts
3. There should be enough Reserve Buoyancy to maintain balance and stability
even with tanks flooded
Basic Concepts
Study CasesP-36 Semi-submersibleRoncador Field off the coast of Brazil
There was deck hull
acting as reserve
buoyancy in
Thuderhorse which
saved it. No reserve
bouyancy available in
P-36.
Thunderhorse Semi-submersibleUS$ 5 Billion, 150 miles offshore of Texas, GoM
HURRICANE DENNISJune 2005 EXPLOSIONMarch 2001
Basic Concepts
4. The platform should stably support the deck above the highest wave crest
Basic Concepts
SHIP NOMENCLATURE
Basic Concepts
SHIP GEOMETRYMoving forward
Basic Concepts
STABILITYStability is the ability of a system to return to its undisturbed position after an
external force is removed (KrishThiagarajan – Handbook of Offshore Str)
Stability
Static
Dynamic
Due to steady wind force
When a sudden gust blows along with steady wind
Basic Concepts
STABILITY1. Transverse Stability
Positively Stable Negatively Stable = Unstable
Basic Concepts
STABILITYMetacenter Point (M)
K = Keel Point
G = Centre of Gravity
B = Centre of Buoyancy
M = Intersection between B and
centerline
GM = Distance between G andGM = Distance between G and
M → Metacenter Height
STABLE, GM > 0
Basic Concepts
STABILITYMetacenter Height (GM)
GM = KB + BM - KG
Second moment of waterplane area about x-axis
Submerged volume
Basic Concepts
STABILITY2. Longitudinal Stability
GMl = KB + BMl - KG
Basic Concepts
STABILITYDYNAMIC 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
FUNCTIONS1. Exploratory Drilling: Drillships, semi-submersible, Jack-ups, barges2. Production and Drilling: Semi-submersibles, Spars, TLs3. Production and Storage: Ship conversions, Newbuild ship & barges4. Pipelaying: Barges, semi-submersibles5. Construction/Derrick Vessels: barges, semi-submersibles5. Construction/Derrick Vessels: barges, semi-submersibles
PARAMETERS TO SELECT FLOATER TYPE
1. Water Depth2. Environment3. Function4. Export by pipeline or tanker
Platform drilling or MODU drilling
Wet or dry tree
Type &function of Floaters
WET & DRY TREESReservoir drivers
Type &function of Floaters
HULL SELECTION CRITERIA
Semi-submersibles
HISTORY
Submersible Semi-Submersible
Before 1971Before 1971
Lack of Consistency in design
Sedco 135 RigPentagone Rig
Semi-submersibles
HISTORY
Submersible Semi-Submersible
Between 1971-1980Between 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 1981-1984Between 1981-1984
Twin Hulls
Well designed bracings
Hull type superstructure
Odyssey
Semi-submersibles
HISTORY
Submersible Semi-Submersible
Between 1984-1998Between 1984-1998
Larger
Deepwater
Harsh Environment
Marine 700
Semi-submersibles
HISTORY
Submersible Semi-Submersible
Between 1999 - 2009Between 1999 - 2009
Ultra Deepwater
Transocean Deepwater Nautilus
Semi-submersibles
HISTORY
Submersible Semi-Submersible
Between 2010 - …..Between 2010 - …..
Ultra Deepwater
Petro Rig 1 – Sembcorp Marine
Semi-submersibles
FUNCTIONSProduction, Drilling &Workover
CAPABILITIESWaterdepth: 80 – 3,000 mWaterdepth: 80 – 3,000 m
Process capacity is up to 180,000 bpd
CURRENT PRESENCENorth Sea, Brazil, Asia, Gulf of Mexico (GoM)
Semi-submersibles
Semi-submersibles
Semi-submersibles
DESIGN PRINCIPLES1 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
TLP TLP
More RigidMore Rigid
(More Fixed)(More Fixed) More CompliantMore Compliant
0 5 10 15 20 25 30
Wave Period (s)
TLP TLP
(heave, roll, (heave, roll,
pitch)pitch)
SemiSemi
Energ
yE
nerg
y
SparSpar
Tension Leg Platform (TLP)
FUNCTIONSProduction, Drilling, Workover& Wellhead Support
Waterdepth: 150 – 1,500 mCAPABILITIES
Process capacity is up to 220,000 bpd
North Sea, West Africa, Gulf of Mexico (GoM)CURRENT PRESENCE
Tension Leg Platform (TLP)
FLOATERS INSTALLED & UNDER CONSTRUCTION
35000
40000
45000
Thunder Horse
AugerUrsa At lant is
Current TLP Depth Limit
0
5000
10000
15000
20000
25000
30000
0 1000 2000 3000 4000 5000 6000 7000
Water Depth, ft.
To
ps
ide
s W
eig
ht,
to
ns Spars
Semis
Mini-TLPs
TLPs
Genesis
Diana
Nept une
Boomvang/ Nansen
Horn Mtn.
Morpeth
Typhoon Mat t erhorn
Devils Tower
Allegheny
Kizomba (E-TLP)
Mars
Ram,/ Powell
Auger
Jolliet
Mar lin
Medusa
Holst ein
MadDog
Gunnison
Marco Polo
Magnolia
Pr ince
Red Hawk
West Senu
Na Kika
Front runner
Minimal Facilities Market
Large Topside
Wet Tree Market
Tension Leg Platform (TLP)
TLP DEVELOPMENT (since 1983 = 25 TLPs)
Tension Leg Platform (TLP)
TYPES OF TLP1. CONVENTIONAL
Shell’s Ram Powell TLP is located in 3,214ft of water at Viosca Knoll, block 956, in the Gulf Of Mexico
Shell’s Brutus TLP during topsides installation in Corpus Christi, TX, in 2001.
Tension Leg Platform (TLP)
TYPES OF TLP2. E-TLP
• Reason for leg extensions
– Wider tendon base for greater pitch
stiffness (stability)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.ABB
Tension Leg Platform (TLP)
TYPES OF TLP3. 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 TLP4. 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 Heave and pitch natural periods less than 4 seconds.
o Minimizing bending loads on TLP deck structure
o Minimizing (pitch-induced) tether tensionso Minimizing (pitch-induced) tether tensions
o Acceptable offset and setdown
o 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 • 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.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
FUNCTIONSProduction, Drilling, Workover, Wellhead Support & Oil Storage
Waterdepth: 150 – 1,500 mCAPABILITIES
Process capacity is up to 220,000 bpd
Malaysia, Gulf of Mexico (GoM)CURRENT PRESENCE
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
FUNCTIONSProduction, Storage & Offloading
Waterdepth: 30 – 3,000 mCAPABILITIES
Process capacity is up to 200,000 bpd
North Sea, North Atlantic, Canada, Mediterranian, Africa, Brazil, AsiaCURRENT PRESENCE
Storage is up to 2 mmbbl
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 SYSTEM1. Turret Moored
INTERNAL
EXTERNAL
2. Spread Mooring
FPSO
MOORING SYSTEM1. Turret Moored
•All mooring lines are attached to turret• All risers routed through turret• Suitable for harsh environment• Disconnection possible• Disconnection possible• Current presence: North Sea, North Atlantic
FPSO
MOORING SYSTEM2. 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 • 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