Types of Offshore Oil Rigs

The United States is the world’s largest consumer of crude oil and it has a policy of lessening its dependence on foreign oil sources. As a result, the future lies in offshore drilling, particularly in the Gulf of Mexico.
According to an article entitled “Journey to the Centre of the Earth” by Matthew Phililps in the March 22, 2010 edition of Newsweek, the U.S. goverment estimates there are 70 billion barrels of oil in the Gulf and, of that total, about 40 billion barrels have yet to be discovered.
However, getting to that oil means that drilling rigs will need to be placed farther offshore than ever before and will need to drill deeper than ever. Today, few offshore rigs have the ability to tap into these huge reserves.
This means that more advancements will need to take place in the more than 100-year history of offshore oil drilling. Following is an overview of the different types of offshore rigs:

Converted land rigs
These were the earliest offshore oil rigs. Drillers placed land rigs on barges and anchored them to the site. Rigs were also built with platforms that reached the sea bottom.

This type of rig is towed out to the desired location and is equipped with legs that are lowered onto the bottom of the ocean. The legs are lowered to the seabed, raising the drilling platform above the waves. This type of offshore rig can search for oil in ocean depths up to about 300 feet.

Like converted land rigs and self-elevating rigs, submersible rigs are good for operating in relatively shallow water. They are towed into position and then the platform is lowered to the seabed.

This type of rig has the advantage of being able to operate in deep water. Like an iceberg, a lot of the rig is hidden from view below the surface. They are anchored to the seabed. These types of rigs, although sophisticated, are not without danger. The Deepwater Horizon, which exploded and sank in the Gulf of Mexico off the coast of Louisiana on Aprii 22, 2010, was this type of rig. The Ocean Ranger, another rig of this type, sank off the coast of Newfoundland on Feb. 15, 1982 after being damaged in a severe storm.

Floating rigs are able to drill in the deepest water – up to about 10,000 feet deep. The ship’s engines keep the rig in place using dynamic positioning (the ship’s propeller’s and thrusters are computer-guided).