Editing Oil platform (section)

===Fixed platforms===
{{Main|Fixed platform}}
[[File:Oil Platform Base Construction.jpg|thumb|right|A fixed platform base under construction on the [[Atchafalaya River]].]]

These platforms are built on [[concrete]] or [[steel]] legs, or both, anchored directly onto the seabed, supporting the deck with space for drilling rigs, production facilities and crew quarters. Such platforms are, by virtue of their immobility, designed for very long term use (for instance the [[Hibernia (oil field)|Hibernia platform]]). Various types of structure are used: steel jacket, concrete [[Caisson (engineering)|caisson]], floating steel, and even [[Offshore concrete structure|floating concrete]]. Steel jackets are structural sections made of tubular steel members, and are usually piled into the seabed. To see more details regarding design, construction and installation of such platforms refer to:<ref>{{Cite web|url=https://www.slideshare.net/amirkabirsadeghi/jsas-002-0401sadeghi|title=An Overview of Design, Analysis, Construction and Installation of Off…|date=October 31, 2013|access-date=July 16, 2019|archive-date=September 29, 2018|archive-url=https://web.archive.org/web/20180929133712/https://www.slideshare.net/amirkabirsadeghi/jsas-002-0401sadeghi|url-status=live}}</ref> and.<ref>{{Cite web|url=https://www.slideshare.net/amirkabirsadeghi/jsas-004-077sadeghi|title=Significant Guidance for Design and Construction of Marine and Offsho…|date=October 31, 2013|access-date=July 16, 2019|archive-date=August 5, 2020|archive-url=https://web.archive.org/web/20200805201618/https://www.slideshare.net/amirkabirsadeghi/jsas-004-077sadeghi|url-status=live}}</ref>

[[Offshore concrete structure|Concrete caisson structures]], pioneered by the [[Condeep]] concept, often have in-built oil storage in tanks below the sea surface and these tanks were often used as a flotation capability, allowing them to be built close to shore ([[Norway|Norwegian]] [[fjord]]s and [[Scotland|Scottish]] [[firth]]s are popular because they are sheltered and deep enough) and then floated to their final position where they are sunk to the seabed. Fixed platforms are economically feasible for installation in water depths up to about {{convert|520|m|abbr=on}}.