Ocean Ranger

Rig:

ODECO Ocean Ranger Semi-Submersible

Date:

15 Feb 1982

Location:

Well J-34, Hibernia Field, North Atlantic

Operator:

Mobil

Fatalities:

84

Introduction

The Ocean Ranger was built for ODECO by Mitsubishu, Japan in 1976 and was one of the largest semi-subs working offshore in the early 1980s. It was approved for 'unrestricted ocean operations' and was designed to withstand extremely harsh conditions at sea, including 100 knot winds and 110 foot waves.

Capsize

In February of 1982, the rig was on hire to Mobil and was drilling the J-34 well in the Hibernia Field, about 166 miles east of Newfoundland. On the night of 14th February, a major Atlantic storm was forecast and the rigs in the Hibernia Field, including the Ranger, prepared for the worsening weather by hanging-off the drillpipe in the well and by disconnecting the rigs from the sub-sea stacks. At about 1900 hours local time, the nearby Sedco 706 experienced a large, powerful wave which damaged some items on deck, including the loss of a life raft. Soon after, radio transmissions from the Ocean Ranger were heard, describing a broken window and water in the ballast control room, with discussions on how best to repair the damage.

At 0052 hours local time, on 15th February, a MAYDAY call was sent out from the Ocean Ranger, noting a severe port list to the rig and requesting immediate assistance. The standby vessel, the Seaforth Highlander was requested to come in close as countermeasures against the 10-15 degree list were proving ineffective. At 0130 hours local time, the Ocean Ranger transmitted its last message: 'There will be no further radio communications from the Ocean Ranger. We are going to lifeboat stations'. In the middle of the night, in the midst of atrocious winter weather, the crew abandoned the rig at around 0130 hours. The rig remained afloat for another 90 minutes, sinking between 0307 hours and 0313 hours local time.

The United States Coast Guard Marine Board of Investigation report into the Ocean Ranger sinking summarised the chain of events leading to the loss of the Ocean Ranger as follows:

  • a large wave appeared to cause a broken portlight;
  • the broken portlight allowed the ingress of sea water into the ballast control room;
  • the ballast control panel malfunctioned or appeared to malfunction to the crew;
  • as a result of this malfunction or perceived malfunction, several valves in the rig's ballast control system opened due to a short-circuit, or were manually opened by the crew;
  • the Ocean Ranger assumed a forward list;
  • as a result of the forward list, boarding seas began flooding the forward chain lockers located in the forward corner support columns;
  • the forward list worsened;
  • the pumping of the forward tanks was not possible using the usual ballast control method as the magnitude of the forward list created a vertical distance between the forward tanks and the ballast pumps located astern that exceeded the suction available on the ballast system's pumps;
  • detailed instructions and personnel trained in the use of the ballast control panel were not available;
  • at some point, the crew blindly attempted to manually operate the ballast control panel using brass control rods;
  • at some point, the manually operated sea valves in both pontoons were closed;
  • progressive flooding of the chain lockers and subsequent flooding of the upper deck resulted in a loss of buoyancy great enough to cause the rig to capsize.

All 84 crew members died, despite concerted attempts by the crews of several standby boats to rescue men from the water. The bodies of 22 of the 84 crew were found in the days after the tragedy and tests concluded that all had died as a result of drowning while in a hypothermic state. No exposure suits were worn and the temperature of the sea water at the time was 29 degrees F (-2 deg Celsuis). The remains of the rig itself were found by sonar search over the following weeks, resting in an inverted position approximately 485 feet south-east of the wellhead, surrounded by major items of debris such as the derrick. The rig had capsized bow-first, turning over and striking the sea floor with the forward ends of the rig's pontoons.

Sources:

U.S. Coast Guard Investigations: Marine Casualty Report PDF document

See also:
Wikipedia: Ocean Ranger.
The Wikipedia article was written by the same author as this article but includes greater detail.

Photos
1. Canadian Heritage Gallery
2. U.S. Coast Guard Investigations: Marine Casualty Report PDF document