Nature of Business

12 Months Ended

Dec. 31, 2011

Nature of Business

Nature of Business

Note 1—Nature of Business

Transocean Ltd. (together with its subsidiaries and predecessors, unless the context requires otherwise, “Transocean,” the “Company,” “we,” “us” or “our”) is a leading international provider of offshore contract drilling services for oil and gas wells.  We specialize in technically demanding sectors of the offshore drilling business with a particular focus on deepwater and harsh environment drilling services.  Our mobile offshore drilling fleet is considered one of the most versatile fleets in the world.  We contract our drilling rigs, related equipment and work crews predominantly on a dayrate basis to drill oil and gas wells.  At December 31, 2011, we owned or had partial ownership interests in and operated 135 mobile offshore drilling units.  As of this date, our fleet consisted of 50 High-Specification Floaters (Ultra-Deepwater, Deepwater and Harsh Environment semisubmersibles and drillships), 25 Midwater Floaters, nine High-Specification Jackups, 50 Standard Jackups and one swamp barge.  In addition, we had two Ultra-Deepwater Floaters and four High-Specification Jackups under construction (see Note 10—Drilling Fleet).

We also provide oil and gas drilling management services, drilling engineering and drilling project management services through Applied Drilling Technology Inc., our wholly owned subsidiary, and through ADT International, a division of one of our U.K. subsidiaries (together, “ADTI”).  ADTI conducts drilling management services primarily on either a dayrate or a completed-project, fixed-price (or “turnkey”) basis.

In February 2011, we sold the subsidiary that owns the High-Specification Jackup Trident 20, located in the Caspian Sea.  In March 2011, we engaged an unaffiliated advisor to coordinate the sale of the assets of our oil and gas properties reporting unit, a component of our other operations segment, which comprises the exploration, development and production activities performed by Challenger Minerals Inc. and Challenger Minerals (North Sea) Limited (together, “CMI”).  As a result of these actions, we reclassified to discontinued operations the operating results associated with our Caspian Sea operations and our oil and gas operations.  Additionally, we reclassified the assets and liabilities of these components as held for sale.  In October 2011, we completed the sale of Challenger Minerals (North Sea) Limited.  See Note 7—Discontinued Operations and Note 28—Subsequent Events.

In October 2011, we completed our acquisition of Aker Drilling, a Norwegian company formerly listed on the Oslo Stock Exchange.  In connection with the acquisition, we acquired two Harsh Environment, Ultra-Deepwater semisubmersibles currently operating on long-term contracts in Norway.  Additionally, we acquired two Ultra-Deepwater drillships currently under construction at the Daewoo Shipbuilding & Marine Engineering Co. Ltd. shipyard in Korea, which have expected deliveries in 2014.  See Note 4—Business Combination.