Editing Offshore construction

{{Short description|Installation of structures and facilities in a marine environment}}
{{Redirect-distinguish|Maritime engineering|Marine engineering}}
{{Broader|Ocean development}}
{{Use dmy dates|date=January 2014}}
{{more citations needed|date=March 2010}}
[[File:Kentish Flats 185488397 729bb056f4 o.jpg|thumb|Offshore wind farm]]
[[File:Oil platform P-51 (Brazil).jpg|thumb|Oil platform]]

'''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.<ref name="Gerwick 2007" />

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]]), whilst [[Floating Production Storage and Offloading|floating structures]] are held in position with substantial [[Mooring (watercraft)|mooring]] systems.<ref name="Gerwick 2007" />

The size of offshore lifts can be reduced by making the construction modular, with each module being constructed [[:wikt:onshore|onshore]] and then lifted using a [[crane vessel]] into place onto the platform.<ref name="Gerwick 2007" /> 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.{{cn|date=August 2021}} 

Specialist floating hotel vessels known as [[flotel]]s 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.{{clarify|what is 'this' high cost activity?|date=August 2021}} 

[[Oil platform]]s are key fixed installations from which drilling and production activity is carried out. [[Drilling rig]]s are either floating vessels for deeper water or [[jack-up]] designs which are a barge with liftable legs.<ref name="P D Handbook" /> 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]]s which define periods of relatively light weather during which continuous construction or other offshore activity can take place. [[Safety]] 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]] are also often a major concern, and [[environmental impact assessment]] may be required during planning. 

The main types of vessels used for [[Submarine pipeline|pipe laying]] are the "[[derrick barge]] (DB)", the "[[pipelay barge]] (LB)" and the "derrick/lay barge (DLB)" combination. [[Closed diving bell]]s in offshore construction are mainly used for [[saturation diving]] in water depths greater than {{convert|120|ft|-1}}, 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 (diving)|launch and recovery system]] (LARS, or "A" frame) on the deck of the rig or a [[diving support vessel]]. The basket is lowered to the working depth and recovered at a controlled rate for decompression. [[Closed bell]]s can go to {{convert|1500|ft}}, but are normally used at {{convert|400|to|800|ft}}.<ref>{{Cite web |title=Offshore Fleet - Pipelaying Vessel |url=http://offshore-fleet.com/data/pipelay-vessel.htm |access-date=2024-08-23 |website=offshore-fleet.com}}</ref> 

Offshore construction includes [[Offshore geotechnical engineering|foundations engineering]], structural design, construction, and/or repair of offshore structures, both commercial and military.<ref name="Gerwick 2007" />

==Outline==
* [[Mariculture]]
** [[Offshore aquaculture]]
* [[Offshore windfarm]]
* [[Floating solar]]
* [[Offshore platform]]<ref name="Gerwick 2007" />
** [[Fixed platform]]s,<ref name="Sadeghi 2007" /><ref name="Sadeghi 2008" />
** [[Spar (platform)]]<ref name="Gerwick 2007" />
** [[Tension leg platform]]<ref name="Gerwick 2007" />
** [[Floating production storage and offloading]]<ref name="Gerwick 2007" /> (FPSOs)
** [[Oil platform]]<ref name="Gerwick 2007" />
** [[Semi-submersible platform]]<ref name="Gerwick 2007" />
** [[Sea fort]]
** [[Accommodation platform]]<ref name="Gerwick 2007" />
** [[Offshore embedded anchors]]
* [[Offshore geotechnical engineering]]
** [[Offshore drilling]]
** [[Land reclamation]]
** [[Artificial island]]
* [[Subsea]]
** [[Submarine pipelines]]<ref name="Gerwick 2007" />
** [[Underwater habitat]]

==See also==
* {{annotated link|Commercial offshore diving}}
* {{annotated link|Fluid mechanics}}
* {{annotated link|Hydraulic engineering}}
* {{annotated link|Hydrology}}
* {{annotated link|Maritime archaeology}}
* {{annotated link|Marine biology}}
* {{annotated link|Oceanography}}
* {{annotated link|Offshore (disambiguation) }}
* {{annotated link|Offshore geotechnical engineering}} 
* {{annotated link|Offshore survey}} 
* {{annotated link|Rheology}}
* {{annotated link|Very large floating structure}}
* {{annotated link|Artificial island}}
* {{annotated link|Underwater habitat}}
* {{annotated link|Ocean development}}
* {{annotated link|Ocean colonization}}
* {{annotated link|Ring crane}}
* {{annotated link|Underground construction}}
* {{annotated link|Wind turbine installation vessel}}

==References==
{{Reflist|refs=

<ref name="P D Handbook">{{cite book|editor=Bevan, John|title=The Professional Divers's Handbook|edition=second|year=2005|publisher=Submex Ltd|location=Alverstoke, GOSPORT, Hampshire|language=en|isbn= 978-0950824260}}</ref>

<ref name="Gerwick 2007" >{{cite book |title=Construction of Marine and Offshore Structures |edition=third |last=Gerwick |first=Ben C. Jr |publisher=Taylor and Francis |date=2007 |isbn=978-0-8493-3052-0 }}</ref>

<ref name="Sadeghi 2007" >{{cite journal |url=http://www.slideshare.net/amirkabirsadeghi/jsas-002-0401sadeghi |title=An Overview of Design, Analysis, Construction and Installation of Offshore Petroleum Platforms Suitable to Cypress/Oil Gas Fields |first=Kabir |last=Sadeghi |journal=J. Soc. & Appl. Sci. |volume=2 |issue=4 |pages=1–16 |date=2007 }}</ref>

<ref name="Sadeghi 2008">{{cite journal |url=http://www.slideshare.net/amirkabirsadeghi/jsas-004-077sadeghi |title=Significant Guidance for Design and Construction of Marine and Offshore structures |first=Kabir |last=Sadeghi |journal=J. Soc. & Appl. Sci. |volume=4 |issue=7 |pages=67–92 |date=2008 }}</ref>

}}

{{Ocean energy}}
{{Engineering fields}}
{{Underwater diving|prodiv}}
{{Authority control}}

[[Category:Coastal construction]]
[[Category:Offshore engineering]]