Cement Failure Contributed to Deepwater Horizon Explosion

By ThinkReliability Staff

The investigation to determine the causes behind the April 20, 2010 explosion of the Deepwater Horizon oil rig and the resulting oil spill is still underway.  (A previous blog discussed the BP report and the initial findings from their investigation.)

The newest piece of information that has come to light is that cement used to seal the production casing wasn’t properly tested.  It was previously assumed that the cement must have failed or the hydrocarbons would not have been able to leak into the well and subsequently feed the massive explosion that destroyed the oil rig.  But more information is coming available that explains why the cement failed.

The well was cemented with nitrogen foam cement supplied by a contractor. Investigation by the presidential commission on the oil spill has revealed that the cement was not properly tested prior to use.  More significantly, the cement was found to be unstable when tested.

 The data indicates that the cement failure was a cause of the oil rig explosion, but was it the root cause?

It’s easy to see that the cement failure was not the only cause.  In addition to the failure of the cement, there were other things that had to occur for the accident to happen.  One of the most obvious is the failure of the blowout preventer.  Even if the cement failed and the hydrocarbons leaked into the well, a functioning blowout preventer would have blocked the leak path for the hydrocarbons and prevented this tragedy.

As with any incident of this magnitude, there is no single root cause, rather there are a number of causes that contributed to the incident.  Determining all the causes that contributed to the incident will allow better understanding of the incident, which will hopefully lead to development and implementation of better solutions to prevent similar accidents in the future.

Mine Deaths in China

By Angela Griffith

Following the successful rescue of all 33 miners trapped in a Chilean mine is some unhappy mine news from China.  A gas blast on October 16, 2010 in the early morning is known to have killed 26 miners, and the 11 miners unaccounted for are believed dead.   In addition to these impacts to the safety goals, the environmental goal is impacted by the extremely high levels of methane gas, the customer service and production goals are impacted by the closure of the mine, and the property and labor goals are impacted by the rescue efforts that have been required.  Unfortunately this is not an uncommon occurrence.  It is estimated that 2,600 people were killed in Chinese mine accidents last year.

It is expected that the miners were mostly killed due to suffocation.  In addition to the lack of oxygen from the extremely high levels of methane (40% compared to the normal level of 1%), the miners were buried by coal dust, released by the gas blast.  The miners were trapped in the mine by the gas blast, of which the cause is as of yet unknown.  This is a question that additional investigation will try and answer.  Additionally more information is needed about the high levels of methane.  The rescuers had difficulty reducing the levels of methane because coal dust was blocking an access shaft, but levels were high prior to the blast, for reasons that are unclear.

More detail can be added to this Cause Map as the analysis continues. As with any investigation the level of detail in the analysis is based on the impact of the incident on the organization’s overall goals.  Because of the high number of deaths (and the high frequency of this type of incident), the Cause Map should end up very detailed in order to provide as many solutions as possible to ensure that the best solutions are implemented to reduce these types of incidents.

Miners Rescued!

By Angela Griffith

On October 13, 2010, after almost 70 days spent at 688 meters underground, the 33 miners who were trapped in Chile’s San Jose Mine were brought to the surface in a small rescue capsule. Although the complexity of this rescue mission was unmatched in history, it seemed to go off without a hitch, even allowing the rescue to proceed more quickly than anticipated.

The primary concern throughout the rescue was the miner’s safety. Plans for the rescue focused on ensuring the safest possible environment for the miners – and making adjustments based on the ordeal they’ve been through. For example, there was concern about damage to the miner’s eyes – they haven’t been exposed to natural light for a while. So the miners wore protective eyewear to prevent damage. In addition, medics and rescuers were sent down to the chamber where the miners had been trapped to prepare them for the trip up (in a rescue pod small enough to fit through a 60-cm diameter hole) and evaluate them for medical conditions. After the miners reached the surface, they will receive 48 hours of medical observation by a team of specialists.

The preparations for this undertaking have been extremely methodical and detail. An area near the mine exit was cleared for a helicopter landing – a backup plan in case anything should happen so that the miners would be unable to be transported to the medical facility by road.

Even less-immediate concerns have been considered. The company that owned the mine went bankrupt while the miners were trapped, meaning these brave men returned to the surface jobless. The Chilean government put out a notice, and has received more than a thousand job offers.

One of the biggest concerns is that the miners will suffer from post-traumatic stress disorder (PTSD). It’s unclear exactly what exactly is being – or can be – done to reduce the impact, but the Chilean government has consulted with NASA about potential emotional and psychological issues the miners will face.

It seems that the rescuers really tried to think of everything that would make the rescue go smoothly – and the result of this planning showed in the faces of millions who watched the last miner safely pulled from the mine. A big Bravo Zulu out to all involved!

(You can see a timeline of the events starting from the mine collapse and a Cause Map that shows some of the worries the rescuers considered – and planned for – by clicking “Download PDF” above.)

Toxic Red Sludge Spill

By Kim Smiley

On Monday, October 4, 2010, a massive wave of red sludge flooded into four villages near Kilontar, Hungary when a storage reservoir burst.  Four were killed and at least 150 have needed medical treatment for their injuries.  The most common injuries reported are burns and eye ailments.

Red sludge is a highly caustic material that is produced during the aluminum manufacturing process.  Reports indicate that the sludge had a pH of 13 while stored in the reservoir.  All life has been killed in a 25 mile stretch of river and 16 square miles of land have been covered by the pollution.  Best estimates are that 158 million to 184 million gallons of sludge were released.  This first large scale release of red sludge in history.

Hungary’s top investigative agency is looking into the accident, but the cause for the reservoir barrier failure is not known at this time.

Even with the unknowns, a root cause analysis can be started by creating a Cause Map and documenting all available information.  Any new information can easily be incorporated into the existing Cause Map.

To build a Cause Map, we start with the impacted goals and ask “why” questions.  In this example, the two goals we will consider are the Safety goal and the Environmental goal.  Starting with the Safety goal we begin by asking – Why were people injured?  They were injured because they were exposed to caustic material because red sludge flooded into their villages.  Why?  Because red sludge was stored in a nearly reservoir and the barrier on the reservoir was breached.

Why the barrier failed isn’t known, but we can still add additional information that might be useful.  We know that the red sludge reservoir was near the villages and a little research reveals that this is common practice in the region and that there are a number of similar pools nearby.  This information may become relevant if the investigation determines that the other reservoirs are at risk for a similar failure so it’s worth recording on our Cause Map at this point. There is also information available about the environmental impact that can be added.

The investigation is still incomplete, but the Cause Map can grow as more information comes available.  Once the relevant information is added, the Cause Map can be used to develop solutions to help prevent similar accidents from occurring in the future.