The leading causes of drilling rig disasters

8 January 2021 (Last Updated January 8th, 2021 14:10)

Rig explosions, fires, capsizing/sinking, oil spills, and the loss of workers and marine lives have been the most catastrophic forms of offshore oil and gas drilling disasters in recorded history. Investigational reports on some of the world’s worst offshore oil rig disasters suggest that most of these accidents could have been avoided. Offshore Technology lists some of the leading causes of drilling rig disasters.

The leading causes of drilling rig disasters
The Deepwater Horizon explosion is the most infamous rig blowout disaster in the recent history.

Rig explosions, fires, capsizing/sinking, oil spills, and the loss of workers and marine lives have been the most catastrophic forms of offshore oil and gas drilling disasters in recorded history.

Investigational reports on some of the world’s worst offshore oil rig disasters suggest that most of these accidents could have been avoided. Offshore Technology lists some of the leading causes of drilling rig disasters.

Blowouts

leading causes of drilling rig disasters
The Deepwater Horizon explosion is the most infamous rig blowout disaster in recent history.

Blowouts are the most common cause of offshore drilling rig explosions and oil spills. Rig blowouts occur when an uncontrolled oil or gas release from the well occurs due to the failure of pressure control systems.

The worst disaster caused by a blowout in recent history is the BP Deepwater Horizon explosion that occurred in April 2010, killing 11 rig workers and spilling more than four million barrels of oil into the Gulf of Mexico.

The other major blowout disasters to have occurred in history include:

  • The Santa Barbara oil spill along the Californian coast in January 1969
  • The Ixtoc I oil spill in the Bay of Campeche of the Gulf of Mexico in June 1979
  • The Enchova Central Platform disaster in the Campos Basin of Brazil, in August 1984
  • The C.P. Baker Drilling Barge disaster in the Gulf of Mexico on 30 June 1964, and
  • The Seadrill’s West Atlas rig disaster in the Timor Sea off the coast of Australia in August 2009.

Strong winds and rouge waves

leading causes of drilling rig disasters
The Alexander L Kielland disaster occurred due to the failure of a bracing attached to one of the five legs of the platform. Credit: Jarvin.

Extreme weather conditions such as typhoons, hurricanes, storms, and rouge waves also lead to explosions, as well as the flooding, capsizing, and sinking of the drilling rigs in the high seas.

The most notable instances of rig capsizing and sinking due to the forceful winds and high waves are the Alexander L Kielland disaster (March 1980) in the Norwegian Continental Shelf that took 123 lives, the Seacrest Drillship disaster (November 1989) in the Gulf of Thailand that killed 91, the Ocean Ranger oil rig disaster (February 1982) in the North Atlantic Sea, Canada that took 84 lives, and the Glomar Java Sea Drillship disaster (October 1983) workers in the South China Sea, Vietnam that claimed 81 lives.

The other major drilling rig disasters caused by natural forces include the Bohai 2 oil rig disaster (November 1979) offshore China that took 72 lives. The incident occurred when the jack-up rig capsized and sank after the fierce winds broke the ventilator pump and caused a puncture hole in the deck, resulting in extensive flooding. As a recent example, the Abkatun Permanente oil platform explosion (August 2015) in the Gulf of Mexico that claimed four lives was caused due to the extreme waves hitting the platform tower.

Collisions

leading causes of drilling rig disasters
The BP Deepwater Horizon explosion occurred due to the failure of the blowout preventer. Credit: Ed Schipul.

Collisions resulting in oil and gas leakages, as well as water flooding, have also been one of the most common causes of drilling rig disasters.

The Mumbai High North disaster (July 2005) in the Arabian Sea, off the western coast of India, that killed 22 people was caused due to collision with a multipurpose support vessel (MSV), resulting in the rupture of the platform’s gas export risers that led to a gas leak and explosion.

The Usumacinta Jack-up disaster (October 2007) in the Bay of Campeche of the Gulf of Mexico, which claimed 22 lives, was also caused due to a collision with the PEMEX-operated Kab-101 platform. This results in a fire due to the leakage of oil and gas as its cantilever deck hit a production valve tree of the platform.

Defective equipment and structural failures

leading causes of drilling rig disasters
Blowouts are the most common causes of offshore oil rig disasters.

While natural disasters remain an inherent risk, faulty equipment and structural defects constitute a major cause of drilling rig disasters. The malfunctioning of equipment and the lack of seaworthiness of the drilling platforms have been attributed as the main reasons for some of the biggest offshore drilling rig disasters.

For example, the capsizing of the Alexander L Kielland platform (March 1980), Norway’s worst offshore disaster that killed 123 people, occurred due to the failure of one of the bracings attached to one of the platform legs to withstand strong winds and high waves. An undetected fatigue crack in the weld of an instrument connection on the bracing was singled out as the root cause of this disaster.

Another example of how the malfunctioning of a single piece of equipment can lead to a full-blown disaster is the Deepwater Horizon disaster, which was caused due to the failure of the blowout preventer. Similarly, the explosions on the Petrobras P-36 semi-submersible oil platform off the coast of Brazil in 2001 were believed to have occurred due to an emergency drain tank, which was ruptured due to increased pressure.

Poor safety procedures

leading causes of drilling rig disasters
The Santa Barbara oil spill along the Californian coast occurred in January 1969. Credit: Doc Searls.

Although surrounded by waters, offshore drilling rigs have a high-risk of fire and explosion due to the nature of the operation. With the high use of flammable materials on and near the rig, a tiny spark or an uncontrolled gas leakage can result in devastating consequences. Offshore drilling, therefore, warrants extraordinary caution and the implementation of proper safety protocols.

The Piper Alpha disaster (July 1988) in the UK North Sea, the world’s deadliest offshore oil rig accident that killed 167 people, was caused due to a communication error that resulted in a tragic safety lapse. As part of routine maintenance, the pressure valve of one of the condensate-injection pumps was removed, and the condensate pipe was temporarily sealed with two blind flanges during shift-change in the evening as the maintenance work was not complete.

Not informed about the removal of the safety valve by the maintenance crew, the night crew, however, turned on an alternate pump. The temporary seal couldn’t handle the pressure, which led to gas leakage followed by ignition and explosions.

Another example of unsafe practices leading to offshore rig disasters is the explosion of the Black Elk Energy production platform that killed three contract workers and spilt oil into the Gulf of Mexico in November 2012. The explosion occurred when a worker tried to weld a pipe near an oil line and the acetylene torch ignited a fire.