Discoverer Seven Seas was built by Mitsui at the Osaka shipyard, Japan and delivered in 1975.
The vessel drilled her first well offshore Ivory Coast and broke her first deepwater record in 1977, drilling the Sanga well offshore Congo in a water depth of 4,400ft (1,341 meters). The record was improved by a few hundred feet while drilling offshore Ibiza, Spain in 1979.
Deepwater records kept coming for a decade:
• 1979, 4,876ft Shell, Canada East Coast
• 1982, 5,624ft, Total, France Mediteranean Sea
• 1983, 6,448ft, Shell, US East Coast
• 1984, 6,952ft, , Shell, US East Coast
• 1987, 7,582ft, Shell US Gulf of Mexico
In 2003 the Discovered Deep Seas, drilling for Chevron in the Gulf of Mexico, became the first to surpass the record of the Discoverer Seven Seas breaking the 10,000 ft barrier with 10,011 ft. In 2013 the ultra-deepwater drillship Dhirubhai Deepwater KG2 set a new record offshore India with 10,385 ft. The actual deepwater record was set in 2014 by the drillship Maersk Venturer drilling the Raya-1 well offshore Uruguay for Total, in a water depth of 11,155 ft.
In January 2015 the Discoverer Seven Seas was idle in Singapore after completing a last drilling campaign offshore Vietnam for Talisman at $400,000 a day. Almost 40 years of operations. Transocean its owner, advised that the drillship will be retired and sold for scrap.