Ocean Ranger - History and Design

History and Design

Ocean Ranger was designed and owned by Ocean Drilling and Exploration Company, Inc. (ODECO) of New Orleans. The vessel was a self-propelled large semi-submersible design with a drilling facility and living quarters. It was capable of operation beneath 1,500 feet (460 m) of ocean water and could drill to a maximum depth of 25,000 feet (7,600 m). It was described by ODECO as the world's largest semi-submersible oil rig to date.

Constructed for ODECO in 1976 by Mitsubishi Heavy Industries in Hiroshima, Japan, Ocean Ranger was 396 feet (121 m) long, 262 feet (80 m) wide, and 337 feet (103 m) high. It had twelve 45,000-pound (20,000 kg) anchors. The weight was 25,000 tons. It was floating on two 122-metre (400 ft) long pontoons that rested 24 metres (79 ft) below the surface.

The vessel was approved for 'unrestricted ocean operations' and designed to withstand extremely harsh conditions at sea, including 100-knot (190 km/h) winds and 110-foot (34 m) waves. Prior to moving to the Grand Banks area in November 1980, it had operated off the coasts of Alaska, New Jersey and Ireland. The joint Federal-Provincial Royal Commission on the Ocean Ranger Marine Disaster found that the crew were not trained, the safety equipment was inadequate, there were no safety protocols for the supply ship, and that the rig itself had a number of design flaws.