The company traces its roots to 1953 when the Birmingham, Alabama-based Southern Natural Gas Company created The Offshore Company after acquiring the joint drilling operation DeLong-McDermott from DeLong Engineering and J. Ray McDermott. In 1954 the company launched the first Jackup rig in the Gulf of Mexico. In 1967 the company went public. In 1978 SNG turned it into a wholly owned subsidiary. In 1982 it was changed to Sonat Offshore Drilling Inc., reflecting a change in its parent's name. In 1993 Sonat spun it off.
In 1996 the company acquired Norwegian group Transocean ASA for US$1.5 billion. Transocean had started in the 1970s as a whaling company and had expanded through a series of mergers. The new company was called Transocean Offshore. The new company began building massive drilling operations with drills capable of going to 10,000 feet (as opposed to 3,000 feet at the time) and operating two drill operations on the same ship. Its first ship, Discoverer Enterprise, cost nearly US$430 million and was 834 ft (254 m). The Enterprise class drillship is the largest of the drilling ships