Platform Technologies for Offshore
Renewable Energy Conversion
Diego Vannucci, RINA
Objectives
DONT RE-INVENT THE WHEEL !
Oil & Gas Industry has been developing offshore technology
for 100 years., is there anything that we can learn ?
Available Offshore Platform Technologies
Fixed Platform
Jacket Structure
Gravity based
Compliant Structures
Guyed towers
Floating Platform
Semi-sub
Tension Leg
SPAR
FPSO
Fixed Platforms: Jacket Structures
The steel jacket type platform on a pile foundation is
by far the most common kind of offshore structure and
they exist worldwide as well as the eldest.
These structures generally support superstructures
having 2 or 3 decks with drilling and production
equipment and workover rigs as well.
The use of these platforms is generally limited to a
water depth of about 150 180 m in the North Sea
environment
Development of Fixed Offshore Structures
At present the record is scored by Bullwinkle jacket installed at a 412 m
water depth.
Fixed Platforms: Gravity Based
Gravity structures are offshore structures that are
placed on the seafloor and held in place by their
weight.
These structures do not require piles or anchors.
Moreover the huge bottom section is quite suited for
production of and storage of oil.
Since gravity base structures require large volume and
high weight, concrete has been the most common
material for gravity structures .
Fixed Platforms: Gravity Based
Because of the nature o these
platforms, they are often prone to
scour of their foundation and sinkage
Fixed Platforms: Compliant Towers
A compliant tower is similar to a traditional jacket
platform and extends from surface to the sea bottom,
and it is fairly transparent to waves. However, unlikely
jacket plkatforms, a compliant tower is designed to flex
with the forces of waves, wind and currents .
The first tower emerged in the early 1980s
Compliant towers are designed to sustain significant
lateral deflections and forces, and are typically used in
water depths ranging from 1,500 and 3,000 feet (450
and 900 m).
At present the deepest is Baldpate in 580 m of water
Floating Platforms: Semi-Submersible
Offshore drilling in high water depth requires that
operations be carried out from a floating vessel, as
fixed structures are not practical
semi-submersible are multi legged floating structures
with a large deck interconnected at the bottom
underwater with horizontal buoyant members called
pontoons.
A semi-submersible obtains its buoyancy from
ballasted, watertight pontoons located below the
ocean surface and wave action.
Todays deepest semisub is Atlantis PQ (-2156 m)
Floating Platforms: Semi-Submersible
The first semi-submersible
arrived in 1961. Blue
Water Drilling Company
owned and operated the
four column submersible
drilling rig Blue Water Rig
No.1 in the Gulf of Mexico
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Floating Platforms: Tension Leg Platforms
A Tension-leg platform or Extended Tension Leg
Platform (ETLP) is a vertically moored floating structure
normally used for the offshore production of oil or gas,
and is particularly suited for water depths greater than
300 metres (about 1000 ft) and less than 1500 meters
(about 4900 ft)
The platform is permanently moored by means of
tethers or tendons grouped at each of the structure's
corners
The first Tension Leg Platform was built for Conoco's
Hutton field in the North Sea in the early 1980s
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Floating Platforms: SPAR
The Spar concept is a large deep draft,
cylindrical floating caisson designed to
support drilling and production operations.
Its buoyancy is used to support facilities
above the water surface. It is generally
anchored to the seafloor with multiple taut
mooring lines
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Floating Platforms: SPAR
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Floating vs. Fixed Offshore Structures
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Fixed Structures: Offshore Renewable Applications
On the surface, it would seem that support structures for OWTs
could be designed based on the design principles used in the oil
and gas industry, however
Contrary to offshore structures, where the dominant loading is
typically from wave loads, offshore wind turbine support
structures may be equally loaded by wind and wave loads
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Offshore Renewable Applications
Technical feasibility of floating structures
has already been successfully , however,
the economics that allowed the
deployment of thousands of offshore
wind turbines have yet to be
demonstrated for renewable energy
conversion platform
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Offshore Renewable: Challanges
100.000 BPD x 100 $/Brl = 10 M$/d
(1500kWx 24h) x 0.10 $/kWh = 3600 $/d
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Offshore Renewable: Opportunities
Re-use of oil platforms
Combination of different re-newable sources
sdcsc
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