A look at Deepwater Horizon

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Bill Cambell

Many commentators around the world talk about the cause of the explosion on Deepwater Horizon when they actually mean the cause of the blowout and subsequent pollution. Blowouts are thankfully rare events; some blowouts in the past have not led to explosions, making recovery efforts more likely to succeed. The fatalities and the total destruction of the installation may have been prevented if an explosion had not occurred.

Occupational Safety vs. Risk Awareness

On Deepwater Horizon at the time of the explosion there was a ceremony in the accommodation module celebrating seven years without a Lost Time Incident. The installation owned and operated by Transocean had an outstanding record of preventing lost time incidents.

Post Piper Alpha, it was recognized that having a low number of lost time incidents, or as was the case on Deepwater Horizon, zero incidents, was no assurance whatsoever that the risks to the health and safety of persons from major accident events on offshore installations were within acceptable limits.

Within the United States the oil industry in recent years was reminded of this. The technical investigation into the Texas City refinery explosion was critical in that whilst BP concentrated on occupational risks, e.g. slips, trips and falls, it paid inadequate regard to the risks of catastrophic events.

The reality was that Deepwater Horizon was a dangerous place for the persons on board regardless of its world class performance in protecting them from occupational injuries.

If the probability of an undesirable event is high, and the consequences of that undesirable event are potentially catastrophic, then the risks are dangerously high. Risk are the product of the probability and the consequence of the event happening. Whether assessed numerically, by Quantitative Risk Analysis, or by Qualitative Risk Analysis, Deepwater Horizon as it operated in the period leading up to the incident had risk levels likely to be in the intolerable range, at levels unacceptable to society, in the weeks prior to the explosion.

Foreseeable and Inevitable?

Due to well control problems a number of significant gas releases into the atmosphere occurred in the weeks prior to the disaster. Allied to this, and from examination of witness testimony, insufficient measures appear to have been in place to prevent gas being ingested into an enclosed non-hazardous area where sources of ignition are constantly present during normal operations.

So the probability that a flammable atmosphere could exist on Deepwater Horizon was high and the probability of subsequent ignition causing an explosion was high. The two combined on the 20th April with catastrophic effect.

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