Drilling Rigs - Semi-Submersible
A Semi-submersible platform or rig, is a mobile structure used for drilling for oil and natural gas in offshore environments. Their superstructures are supported by columns sitting on hulls or pontoons which are ballasted below the water surface. They provide excellent stability in rough, deep seas. Semi-submersible rigs can be moved from place to place; and can be ballasted up or down by altering the amount of flooding in buoyancy tanks; they are generally anchored by cable anchors during drilling operations, though they can also be kept in place by dynamic positioning. Semi-submersibles can be used in depths from 600 up to 35,000 feet (180 to more than 10,600 m).
Dana's Western Isles FPSO
Sevan design WI FPSO during offload at the Caland Kanal, Europoort 19/04/2017 prior to docking at Ke...
Brent D 1980
Approaching to land on Delta's very hot heli-pad in late April-early May 1980.
Ninian Central Platform
NCP with accommodation platform Bredford Dolphin in the late '70's but am unsure of exact date.