The Justice Department made the announcement Thursday.
The offshore drilling firm owned and provided a crew for the Deepwater Horizon rig, where an explosion killed 11 men.
It also triggered the worst maritime oil spill in U.S. history.
Transocean was contracted by BP, which leased the rig and directed staff on board.
BP agreed in November to plead guilty to criminal charges and pay four-point-five billion in penalties.