The Sea Gem was the first British offshore oil rig, and the first British offshore rig disaster when in 1965, the rig's legs collapsed, killing 13 of the crew.
In the early 1960s, oil companies had found some crude oil in Great Britain, as well as in the Netherlands and Germany, and suspected that there was more to be found under the North Sea. Unfortunately there were some barriers that had to be overcome before it was to be possible to search for oil and gas.
First of all, there had been no international agreements that addressed the rights to the various minerals and areas outside the three mile (5 km) limit. Also, the technology required was not yet developed, or hadn't matured enough to be commercially usable.
The main factor, however, was that the oil companies generally didn't think that there were significant enough reserves in the North Sea to warrant the usage of resources to search for oil. This situation changed however, when fields such as Groningen in the Netherlands, and to a certain extent Eakring in the UK, proved to contain fairly large reserves, thus prompting the oil companies to begin a search in nearby areas, including the North Sea.
The Sea Gem made the first British discovery of natural gas in September 1965, although the find was too small to be commercially profitable.
The Sea Gem was originally a 5,600 ton steel barge, converted to function as an oil rig by British Petroleum in 1964. The barge basically consisted of 10 steel legs which made it possible to raise the barge 15 metres (49 ft) over the water's surface, as well as a helipad, living quarters for the crew of 34 and a drilling tower with associated structures.
On 27 December 1965, the rig was located approximately 67 kilometres (42 mi; 36 nmi) off the coast of Lincolnshire. The crew were in the process of moving the rig to another site approximately 2 nautical miles (3.7 km; 2.3 mi) away. This process involved lowering the rig onto the surface of the water, in order to float it to the new site. When the rig was lowered, two of the legs crumpled and broke, causing the rig to capsize, with equipment and people sliding off and into the freezing cold of the North Sea at 1409 GMT.
As the radio hut was among the equipment that fell into the sea, the rig never sent out an emergency signal. Luckily the nearby British freight ship the Baltrover observed the capsizing. The crew on Baltrover sent out emergency signals and proceeded to help rescue the crew together with a RAF and a civilian helicopter.
As a result of a public inquiry into the accident, several changes were made in order to improve the safety of oil rigs, amongst them the use of a stand-by boat, which would be able to help rescue crews in the event of future accidents, and the recognition of an Offshore Installation Manager.
This inquiry concluded metal fatigue in part of the suspension system linking the hull to the legs was to blame for the collapse.
- 1965: Sea Gem oil rig collapses. BBC
- Inquiry into the Causes of the Accident to the Drilling Rig Sea Gem, Adams, J.R. (1967), The Ministry of Power, HMSO CM3409, London