Oil Rig Accidents: Semi-Submersible Accidents

Fatalities and serious injuries are relatively common among oil rig workers, whether working onshore or offshore. According to CDC, the fatality rate in this professional field is seven times higher than the national average for all US workers.

There are various risks for the people who work either on a fixed semi-submersible drilling rig or a mobile offshore drilling unit. The type of the platform could contribute to some specific risks that should be evaluated and addressed accordingly to reduce the danger for workers.

Semi-Submersible Platform Risk Factors

Semi-submersible vessels and platforms appeared for the first time in the early 21st century. Shell Company is seen as the pioneer in the field. Originally, these platforms were created for use in shallow waters. Later on, platforms with ballasted pontoons were created for use in deeper water. Anchoring is provided through the use of massive steel cables.

Various risks stem from the use of such platforms, especially when they’re being operated in deep waters.

There have been instances of semi-submersible platforms collapsing and sinking. These have been susceptible to severe weather, as well. Whenever a platform capsizes in deep waters, the loss of life is almost entirely unavoidable.

Structural design issues, wear, and tear, could potentially contribute to risks, as well. While fatigue analysis has increased in precision over the years, many environmental factors will still have to be taken into consideration to pinpoint adequate safety measures.

A couple of the most common risks that such rigging facilities could eventually be vulnerable to include:

  • Loss of stability
  • Loss of watertight integrity
  • Structural failure
  • Gas and oil leaks that increase the risk of explosions
  • Mooring or dynamic positioning (DP) failure
  • Loss of well integrity and a subsequent blowout

Most Prominent Semi-Submersible Platform Accident

Over the years, numerous prominent accidents have made headlines because of the immense loss of human life linked to those.

One of the most prominent disasters occurred in 1982 when a Mobil Oil drilling unit called Ocean Ranger sank. The unit was exploring 166 miles off the coast of Newfoundland in a major storm.

When a hurricane hit, the crew decided to abandon Ocean Ranger. Rescue efforts, however, were horrendously planned. As a result, all of the 84 crew members were killed in the sinking of the unit.

Another major disaster occurred in the Gulf of Mexico in 1979. A semi-submersible rig was drilling the Ixtoc I exploratory oil well. On June 3, the well suffered a massive blowout that caused an unprecedented oil spill. Initially, the well leaked 30,000 barrels of oil into the gulf per day. While numerous efforts were undertaken to contain the environmental disaster, the oil leakage continued until March 1980.

One of the newest deadly accidents involving such a platform occurred in the North Sea in 2016. The winter storm Frank had been hitting the area for a couple of days, which made various companies including British Petroleum stop operations.

Eventually, a China Oilfield Services semi-submersible rig was hit by the bad weather. A wave hit it at a time when it had taken off from a well. The accident killed one worker and injured two others.

While there aren’t newer reports about serious injuries or fatalities involving Gulf of Mexico platforms, accidents of a serious magnitude have taken place in other parts of the world. In 2012, a semi-submersible drilling unit called Stena Clyde was located approximately 62 miles away from Victoria’s (Australia) Port Campbell. Eventually, the drill string got stuck in a hole. All efforts to free it failed and the crew decided to begin wireline operations.

In the preparatory phase, two workers were struck by the top drive and killed by their injuries. Stena Drilling, the owner of the facility, eventually pleaded guilty, acknowledging that it had failed to provide safe working conditions for the workers.

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