††An oil rig is a drilling platform anchored offshore and used for obtaining oil from under the sea-bed.
With the advent of offshore drilling for oil in 1900, the need to build oil rigs emerged. The earliest kind of drilling rig stood on rigid legs which were fixed to the sea-bed. Some of these fixed-leg rigs are as tall as the Empire State Building in New York.
Today mobile semi-submersible rigs are used to find oil under the sea. These can then be replaced by fixed rigs when a site has been identified. An oil rig may be in a very isolated or dangerous place, and its workers usually stay on it for many months.
In the early 1960s, new reserves of oil and gas were found beneath the North Sea off the British coast. In particular, there was enough gas to comfortably supply the British Isles for some time. Work continues today, and there may .yet be undiscovered supplies. Oil rigs are now some of the largest structures ever built and they can contain living quarters for 300 workers.
