Transocean Ltd has announced that its ultra-deepwater semi-submersible rig, Deepwater Horizon, has drilled the deepest oil and gas well ever while working for BP and its co-owners on the Tiber well in the US Gulf of Mexico. Working with BP, the Transocean crews on the Deepwater Horizon drilled the well to 35,050ft vertical depth and 35,055ft measured depth while operating in 4130ft of water. The Deepwater Horizon, placed into service in 2001, is a dynamically positioned ultra-deepwater semi-submersible rig capable of working in water depths of up to 10,000ft.