Transocean operated the Deepwater Horizon drilling rig when it exploded in 2010. The mobile offshore drilling unit was owned and operated by Transocean and was working under contract for BP on the Macondo well in the Gulf of Mexico.
On April 20, 2010, an explosion killed 11 workers and injured others. The rig later sank, and oil flowed from the damaged well for months. BP was the well’s operator and was chiefly associated with responsibility for the resulting environmental disaster, while Transocean owned and operated the rig and Halliburton performed cementing work.
The distinction between the companies matters because several firms faced investigations, lawsuits, and penalties. The disaster led to extensive reforms in offshore drilling regulation and became the largest marine oil spill in the history of the petroleum industry.