2015 ARKH-P4-2 Floating Supports

ARKHANGELSK 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
	Powell

	• Hull : Belleli (Italy)			•	Hull : Belleli (Italy)
	•	Deck : Mc Dermott		•	Deck : Mc Dermott in Louisiana
	•	Tendons and piles : Aker		•	Tendons and piles : Aker
				•	Oil line (12 inch)
				•	Gas line (14 inch)
				•	25 miles pipelines .

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