balder gulf mexico

Transcription

balder gulf mexico
Subsea installation in
extreme water depths
– a contractor’s view
Kees van Zandwijk
Heerema Marine Contractors SE
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Objective of the paper
ƒ Explore when steel wires are better for
deepwater lowering and when fiber ropes
ƒ Vary
– vessel type: crane vessel, OSV
– object lowered: suction pile, template
– sea conditions: Gulf of Mexico, Norway,
Angola
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Historical development of DWL
ƒ 1990 - 1995
Tension leg platforms
<500t / 1000m
Crane vessels
ƒ 1995 - 2005
Floating production facilities
<500t / 2000m
DWL systems
ƒ 2005 - today
Subsea production units
2000t? / 3000m?
New DWL investments?
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Reach deeper at less capacity
T
T
T
h
2h
Wire length = 2 x 6 x h = 12h
Capacity = 2 x 6 x Twire = 12Twire
T
Wire length = 2 x 3 x 2h = 12h
Capacity = 2 x 3 x Twire = 6Twire
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Traction winch for steel wires
F = 60 T
traction winch
F = B * eμα
B = 3 T
storage reel
gas spring
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Capacity of steel wires vs. depth
Effectiveness [%]
0
0
20
40
60
80
100
‐500
‐1000
Water depth [m]
‐1500
steel wires
fiber ropes
‐2000
‐2500
‐3000
‐3500
‐4000
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Traction winch for fiber ropes
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CAPEX of DWL system
CAPEX steel wire vs. fiber rope
steel wires
fiber ropes
0
1000
2000
3000
4000
Water depth [m]
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Fiber ropes enable use of OSV
Steel wire DWL system
Fiber rope DWL system
1500t
500t
500t
500t
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OPEX to consider three aspects
Day rate of installation vessel x Net duration of activity
OPEX = Operability of activity
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Balder installing suction piles
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Deepwater lowering
1. Over-boarding
2. Passing the waterline
3. Lowering to depth
4. Landing on the seabed
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LiftDyn analysis of operability
Balder
with
suction pile
OSV
with
suction pile
Balder
with
template
150t
150t
1700t
0m
1000m
2000m
3000m
Structure landing speed < 0.5 m/s
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Three typical wave spectra
Norwegian Sea
Aasta Hansteen
West of Africa
Angola Block 31
Tp [s]
Tp [s]
Tp [s]
Hs [m]
Gulf of Mexico
Perdido
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Hs [m]
Determine operability
versus wave spectra
Gulf of Mexico
Perdido
Norwegian Sea
Aasta Hansteen
West of Africa
Angola Block 31
Non‐
operable
Non‐
operable
Non‐
operable
Operable
Operable
Operable
Tp [s]
Tp [s]
Tp [s]
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Operability Balder on suction pile
No Active Heave Compensation
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Operability OSV on suction pile
No Active Heave Compensation
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Operability OSV on suction pile
With Active Heave Compensation
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Operability Balder on template
No Active Heave Compensation
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Elastic stretcher
ƒ Nylon versus fiber rope:
– Nylon strength 3x weaker Æ 3x more A
– Elasticity of nylon 30x lower Æ 30x lower E
– Æ k = EA/L of nylon 10x lower than fiber rope
ƒ Nylon stretcher of 100m has same effect
as 1000m fiber rope
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Operability Balder on template
No Active Heave Compensation
100m nylon
stretcher
200m nylon
stretcher
300m nylon
stretcher
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Conclusions [1]
ƒ Crane vessels do very well using steel
wires. In specific situations, an elastic
stretcher of limited length may enhance
the operability.
ƒ An OSV installing a suction pile has a
reasonable operability only when using
fiber ropes and active heave
compensation
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Conclusions [2]
ƒ An investment in a steel wire or fiber rope
DWL system should consider:
– type of installation activities (also non-DWL
activities)
– water depth of operation
– wave regime
– installation vessel
Sometimes fiber ropes are better,
sometimes steel wires
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Contact information
Kees van Zandwijk
cvanzandwijk@hmc-heerema.com
Radboud van Dijk
rvandijk@hmc-heerema.com
Eelco Harmsen
eharmsen@hmc-heerema.com
Heerema Marine Contractors SE
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