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).
Henry Goodrich Dwarfing the ferry on the Cromarty Firth in northern Scotland, the HENRY GOODRICH is a Sonat/Mitsui ...
Vessel passing A cable laying vessel, the Apache, passing a rig anchored in the Cromarty Firth.
Frontier Driller This is the Frontier Driller, ex KNV, ex Transocean Explorer being towed out of the Cromarty Firth b...
Pentagon at Puerto Madryn, Argentina I was sent out to Argentina to inspect this rig in 1995. It was eleven years old but had only been u...
Line of Rigs in the Cromarty Firth Only a few years ago as many as 18 rigs at a time were anchored in the safety of the Cromarty Firth....
Jack Ryan Drillship © BP plc
Transocean Wildcat Moored off Invergordon in the Cromarty Firth
Transocean Wildcat Transocean Wildcat cold-stacked in the Cromarty Firth
Oil rig in the fog On a foggy morning in Cromarty this photo was made. 
