Ranger I

Rig:

Atlantic Pacific Marine Corp. Ranger I

Date:

10 May 1979

Location:

Block 189L, Gulf of Mexico

Operator:

Mitchell Energy Offshore Corp.

Summary

The Ranger I, a jack-up workover barge, was built in 1968 and consisted of an upper hull supported by three cylindrical legs fixed to support mat. After having spent 2 months in an Alabama shipyard in the spring of 1979, the rig was towed to a new drilling location in Block 189L. Once on location, the rig was jacked up, pre-loaded and the derrick skidded into position. Operations on the new well began on 10th May 1979 with the installation of the conductor.

The first sign of possible trouble occurred between 1500 and 1800 hours on the afternoon of 10th May. The Ranger I experienced a violent shudder, with personnel reporting it as a violent shaking or a vertical fall of up to 30cm. Up to an hour was spent trying to locate the cause of the movement without success. Work aboard the rig then continued, including the offloading of supplies from the Delta Seahorse supply boat.

At about 2230, prior to a shift change, the Ranger I collapsed into the sea. The stern leg, below the accommodation block, broke near the connection to the support mat causing the upper hull to fall stern-first and strike the Delta Seahorse. The bow legs supported the upper hull for a short time, then collapsed, allowing the upper hull to fall to the sea. The upper hull then separated from the legs, drifted to the west and sank over the course of the following day.

Prior to the initial collapse, most of the crew were in the living quarters, with 13 men in the galley. The survivors reported experiencing a rapid fall followed by sudden jolt as the upper hull struck the water. The lower floor of the accommodation unit flooded instantly to a depth of 2-3 feet. The men escaped either through the galley's port door or through galley windows taking seat cushions or life jackets for floatation. Three patterns developed: one group gathered at the helideck; a second group swam to the Delta Seahorse whilst a third jumped overboard to get away from the upper hull before it sank.

The Delta Seahorse, alongside the Ranger I, signaled a MAYDAY and picked up four crew from the water, going on to co-ordinate further rescue operations. The Miss Angela, busy towing another rig at the time of the collapse, was also dispatched to aid the rescue and picked up a further 14 men. Coast Guard helicopters recovered another four men from the water. Eight men lost their lives in the accident, with many of the survivors suffering serious injuries.

The remains of the rig were later salvaged and examined by the U.S. Coast Guard. The investigating board concluded that the Ranger I had collapsed as a result of an existing fatigue crack in the stern leg, near the connection to the mat. At around 1700 hours on 10 May 1979, the crack had rapidly propagated around the leg, causing the leg to break and the rig to shudder. Over the following hours, a combination of dynamic and static loading dislodged the broken leg and caused the rig to collapse.

Sources:

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

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