Offshore Construction
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Offshore construction is the installation of structures and facilities in a marine environment, usually for the production and transmission of electricity, oil, gas and other resources. It is also called maritime engineering. Construction and pre-commissioning is typically performed as much as possible onshore. To optimize the costs and risks of installing large offshore platforms, different construction strategies have been developed. One strategy is to fully construct the offshore facility onshore, and tow the installation to site floating on its own buoyancy. Bottom founded structure are lowered to the seabed by de-ballasting (see for instance Condeep or
Cranefree Cranefree is the trademark for offshore foundations marketed by the company Seatower.http://seatower.com/ This technology is focused on the offshore wind sector, and is designed to avoid using heavy-lift crane vessels in order to make offshore ...
), whilst
floating structures Floating may refer to: * a type of dental work performed on horse teeth * use of an isolation tank * the guitar-playing technique where chords are sustained rather than scratched * ''Floating'' (play), by Hugh Hughes * Floating (psychological ...
are held in position with substantial
mooring A mooring is any permanent structure to which a vessel may be secured. Examples include quays, wharfs, jetties, piers, anchor buoys, and mooring buoys. A ship is secured to a mooring to forestall free movement of the ship on the water. An ''an ...
systems. The size of offshore lifts can be reduced by making the construction modular, with each module being constructed onshore and then lifted using a
crane vessel A crane vessel, crane ship or floating crane is a ship with a crane specialized in lifting heavy loads. The largest crane vessels are used for offshore construction. Conventional monohulls are used, but the largest crane vessels are often catam ...
into place onto the platform. A number of very large crane vessels were built in the 1970s which allow very large single modules weighing up to 14,000 tonnes to be fabricated and then lifted into place. Specialist floating hotel vessels known as flotels or accommodation rigs are used to accommodate workers during the construction and hook-up phases. This is a high cost activity due to the limited space and access to materials.
Oil platform An oil platform (or oil rig, offshore platform, oil production platform, and similar terms) is a large structure with facilities to extract and process petroleum and natural gas that lie in rock formations beneath the seabed. Many oil platfor ...
s are key fixed installations from which drilling and production activity is carried out.
Drilling rig A drilling rig is an integrated system that drills wells, such as oil or water wells, or holes for piling and other construction purposes, into the earth's subsurface. Drilling rigs can be massive structures housing equipment used to drill wa ...
s are either floating vessels for deeper water or jack-up designs which are a barge with liftable legs. Both of these types of vessel are constructed in marine yards but are often involved during the construction phase to pre-drill some production wells. Other key factors in offshore construction are the
weather window A weather window occurs when weather forecasts indicate that a given set of marine operations or offshore construction activities can be performed within their maximum limits for wave height, wind speeds etc. Critical elements for offshore operat ...
s which define periods of relatively light weather during which continuous construction or other offshore activity can take place.
Safety Safety is the state of being "safe", the condition of being protected from harm or other danger. Safety can also refer to the control of recognized hazards in order to achieve an acceptable level of risk. Meanings There are two slightly di ...
of personnel is another key construction parameter, an obvious hazard being a fall into the sea from which speedy recovery in cold waters is essential.
Environmental issues Environmental issues are effects of human activity on the biophysical environment, most often of which are harmful effects that cause environmental degradation. Environmental protection is the practice of protecting the natural environment on t ...
are also often a major concern, and
environmental impact assessment Environmental Impact assessment (EIA) is the assessment of the environmental consequences of a plan, policy, program, or actual projects prior to the decision to move forward with the proposed action. In this context, the term "environmental imp ...
may be required during planning. The main types of vessels used for pipe laying are the " derrick barge (DB)", the "
pipelay barge A pipelaying ship is a maritime vessel used in the construction of subsea infrastructure. It serves to connect oil production platforms with refineries on shore. To accomplish this goal a typical pipelaying vessel carries a heavy lift crane, use ...
(LB)" and the "derrick/lay barge (DLB)" combination. Closed diving bells in offshore construction are mainly used for saturation diving in water depths greater than , less than that, the surface oriented divers are transported through the water in a wet bell or diving stage (basket), a suspended platform deployed from a launch and recovery system (LARS, or "A" frame) on the deck of the rig or a
diving support vessel A diving support vessel is a ship that is used as a floating base for professional diving projects. Basic requirements are the ability to keep station accurately and reliably throughout a diving operation, often in close proximity to drilling or ...
. The basket is lowered to the working depth and recovered at a controlled rate for decompression. Closed bells can go to , but are normally used at . Offshore construction includes foundations engineering, structural design, construction, and/or repair of offshore structures, both commercial and military.


Outline

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Mariculture Mariculture or marine farming is a specialized branch of aquaculture (which includes freshwater aquaculture) involving the cultivation of marine organisms for food and other animal products, in enclosed sections of the open ocean ( offshore m ...
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Offshore aquaculture Offshore aquaculture, also known as open water aquaculture or open ocean aquaculture, is an emerging approach to mariculture ( seawater aquafarming) where fish farms are positioned in deeper and less sheltered waters some distance away from the ...
* Offshore windfarm * Floating solar *
Offshore platform An oil platform (or oil rig, offshore platform, oil production platform, and similar terms) is a large structure with facilities to extract and process petroleum and natural gas that lie in rock formations beneath the seabed. Many oil platfor ...
** Fixed platforms, ** Spar (platform) ** Tension leg platform **
Floating production storage and offloading A floating production storage and offloading (FPSO) unit is a floating vessel used by the offshore oil and gas industry for the production and processing of hydrocarbons, and for the storage of oil. An FPSO vessel is designed to receive h ...
(FPSOs) **
Oil platform An oil platform (or oil rig, offshore platform, oil production platform, and similar terms) is a large structure with facilities to extract and process petroleum and natural gas that lie in rock formations beneath the seabed. Many oil platfor ...
** Semi-submersible platform **
Sea fort 300px, Castillo San Felipe de Barajas in Cartagena de Indias, Colombia, an example of an Early Modern coastal defense Coastal defence (or defense) and coastal fortification are measures taken to provide protection against military attack at or ...
**
Accommodation platform An accommodation platform is an offshore platform which supports living quarters for offshore personnel. These are often associated with the petroleum industry, although other industries use them as well, such as the wind farm Horns Rev 2.
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Offshore geotechnical engineering Offshore geotechnical engineering is a sub-field of geotechnical engineering. It is concerned with foundation design, construction, maintenance and decommissioning for human-made structures in the sea.Dean, p. 1 Oil platforms, artificial island ...
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Offshore drilling Offshore drilling is a mechanical process where a wellbore is drilled below the seabed. It is typically carried out in order to explore for and subsequently extract petroleum that lies in rock formations beneath the seabed. Most commonly, the t ...
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Land reclamation Land reclamation, usually known as reclamation, and also known as land fill (not to be confused with a waste landfill), is the process of creating new land from oceans, seas, riverbeds or lake beds. The land reclaimed is known as reclamat ...
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Artificial island An artificial island is an island that has been constructed by people rather than formed by natural means. Artificial islands may vary in size from small islets reclaimed solely to support a single pillar of a building or structure to those th ...
* Subsea ** Submarine pipelines **
Underwater habitat Underwater habitats are underwater structures in which people can live for extended periods and carry out most of the basic human functions of a 24-hour day, such as working, resting, eating, attending to personal hygiene, and sleeping. In thi ...


See also

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References

{{Authority control Coastal construction Offshore engineering