2015 ARKH-P4-2 Floating Supports
.pdfARKHANGELSK STATE TECHNICAL
UNIVERSITY
OFFSHORE FIELD DEVELOPMENT PROCESS,CONCEPTS
AND FACILITIES
OCT 2015
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PART 4.2: OFFSHORE PRODUCTION FACILITIES FLOATING SUPPORTS –TLPs, SPARs,SEMIs
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Daniel Saincry
Deep waters system types
Fixed platforms |
TLP |
Semi sub |
Spar |
FPSO |
Dry tree |
Wet tree |
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Dry tree versus wet tree
DRY TREE
The wellhead X-tree is on a deck, above sea level (dry environment)
WET TREE
The wellhead X-tree is on the sea level
Advantages of DRY TREE
Conventional drilling technology (threaded pipes)
Direct access for maintenance
Direct access for connections of pipes and commands (no robot)
Drawbacks of DRY TREES (Ultra deep offshore) = RISERS
Difficulties in tensioning (weight and added elongation)
Fatigue
Difficulties to tie back
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TLP’s
Fixed platforms |
TLP |
Semi sub |
Spar |
FPSO |
Dry tree |
Wet tree |
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The TLP concept : pulled down Unit
Buoyancy
Lateral excursion
Vertical tension
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Evolution of TLPs (Tension legs platforms)
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Tension Leg Platform motions
Low pitch and roll motions, and very low vertical heave amplitude (natural periods 2 to 4 sec)
Exemple: for largest GOM hurricane waves of 25 m, the corresponding vertical motion of TLP is only a few centimeters !
Mooring compliant for lateral motions such as surge & sway with long natural periods 80 to 120 sec
Horizontal excursion in the range of 5 to 6 % of the WD
TLP moves laterally under wind/waves/current forces : OFFSET Offset is accompanied by an increase of TLP draft : SETDOWN
When TLP is offset, tendon tension react to bring TLP back to initial position
Principle schematic
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Lateral offset set-down floater
TLP tendon mooring system
Tendons are highly tensioned by excess buoyancy of hull
Tendon
top connector
Flexjoint
Bottom tendon connector
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Classic TLPs
Ursa
TLP
Towing of the TLP to the field
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Classic TLPs
Mars |
Ram |
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Powell |
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• Hull : Belleli (Italy) |
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Hull : Belleli (Italy) |
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Deck : Mc Dermott |
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Deck : Mc Dermott in Louisiana |
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Tendons and piles : Aker |
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Tendons and piles : Aker |
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Oil line (12 inch) |
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Gas line (14 inch) |
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25 miles pipelines . |
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