Tharos
Transocean Marianas
Semi-submersible drilling vessel
Transocean Marianas was an Earl & Wright Sedco 700 design semi-submersible platform drilling unit capable of operating in harsh environments and water depths up to 7,000 feet (2,100 m) using an 47.6 cm (18.75 in), 15,000 psi blowout preventer (BOP), and a 53 cm (21 in) outside diameter (OD) marine riser.[3]
Transocean Marianas has operated under several names: Tharos from 1979 to 1994, Polyportia from 1994 to 1996, and P. Portia from 1996 to 1998.
On October 7, 2009, it began drilling on the Macondo well in the Gulf of Mexico. On November 9, 2009. it was damaged by Hurricane Ida. It was subsequently replaced by the Deepwater Horizon, which was responsible for the Deepwater Horizon oil spill when that rig exploded on April 20, 2010.[4]