Tag Archives: oil rig

Root Cause Analysis - Incident Investigation

Combination of Gas Leak and Flare Could be Disastrous

By ThinkReliability Staff

A leak from the Elgin platform in the north sea near Aberdeen has the potential to cause an explosion due to the proximity of the leak to the still-lit flare on the platform.  However, the wind is currently blowing gas away from the flare.  The potential for environmental damage is not as great as that of Deepwater Horizon because it is a surface, rather than underwater, leak.

Workers on the now-evacuated Elgin rig noticed the leak on March 25, 2012.  The rig was partially, then later fully, evacuated.  We can examine the causes of the environmental leak, as well as the potential for further damage, in a visual root cause analysis in the form of a Cause Map.  The Cause Map lays out the cause-and-effect relationships in a clear, intuitive way.

We begin with the impacts to the goals.  The safety goal is impacted because of the potential for an explosion.  The environmental goal is impacted due to the gas leak, estimated to be approximately 200 cubic metres per day.  The customer service goal is impacted due to the loss of value of the owner corporation stock shares.  Production is currently shut down on the rig, leading  to an impact to the production goal.  The potential for an explosion could also cause catastrophic damage to the platform, which is an impact to the property goal.  Lastly, the evacuation of the platform is an impact to the labor goal.

In order for an explosion to occur, there must be fuel, oxygen, heat and confinement.  In this case, the oxygen is provided by the atmosphere, and the confinement is provided by the well itself.  The fuel is provided by the gas leak, believed to be entering from another non-producing well through a crack in the outer casing of the well, which was in the process of being plugged and abandoned.    The heat likely to cause the explosion is a flare on the platform.  The flare burns off excess gas from the platform and was not extinguished during the evacuation, as the priority was to remove the workers.

The flare is unable to be turned off remotely, but options for extinguishing the flare are being evaluated.  Other options being evaluated to stop the leak and reduce the potential for explosion include digging a relief well or killing the well that is currently leaking.  All options have the potential to be very expensive.

To view the Outline and Cause Map, please click “Download PDF” above.

Root Cause Analysis - Incident Investigation

Containment Cap Removed from Gulf Oil Leak

By ThinkReliability Staff

Last Wednesday, another set back occurred in the attempt to stem the flow of oil in the Gulf of Mexico from the a well head that was damaged when the Deepwater Horizon Oil Rig exploded on April 20 and sank 36 hours later .

The containment cap used to siphon oil from the damaged well head for the last three weeks had to be temporarily removed for more than 11 hours.  Before being removed, the containment system was sucking up about 29,000 gallons an hour.

So what happened?  Why remove a containment cap that had been working successful?

A root cause analysis of this problem can be built as a Cause Map.  A Cause Map is started by considering the impact to the goals and asking “why” questions to add Causes.  In this example, the first goal we will consider is the Environmental Goal.  Obviously, the environmental goal is impacted because there was additional oil released to the environment because the cap was removed.

Continuing to ask “why” questions we can add additional causes.  The cap was removed because the ship connected to the containment cap system needed to be moved away from the well because there a safety concern because of the potential for an explosion.

There was an explosion concern because there was evidence that flammable gas was flowing up from the well head because liquid was being pushed out of a valve in the containment system.  This gas was getting into the containment cap system because an underwater vent was bumped by one of the remote-controlled submersible robots being used to monitor the damaged well.

More detail could be added to the Cause Map by continuing to ask why questions.  The detailed Cause Map could then be used to develop solutions that could be implemented to help prevent the problem from reoccurring.

Click on the “Download PDF” button above to view an initial Cause Map.

The containment cap was put back into place around 9 pm on June 23.  The efforts to contain and clean up the oil spill will continue for months and possibly years to come, but at least this small issue has been fixed.

Root Cause Analysis - Incident Investigation

Oil Rig Explosion

By ThinkReliability Staff

On April 20, 2010 about 10 pm a huge explosion rocked a semi-submersible drilling oil rig about 40 miles off the coast of Louisiana in the Gulf of Mexico. The oil rig was called the Deepwater Horizon and was owned by Transocean Ltd and leased to the British Petroleum Company through September 2013.

The oil rig burned for about 36 hours before sinking.  126 people were on the oil rig at the time of the explosion.  Eleven are missing and presumed dead and 4 were critically injured. Oil continues to leak from the wellhead more than a mile underwater on the ocean floor at an estimated rate of 42,000 gallons a day.

Remotely operated submersible vehicles were used to examine the wellhead.  The vehicles were also used in an effort to manually trigger the blowout preventer, which would close the wellhead and prevent any farther release of oil.  The blowout preventer is a 450-ton valve installed at the wellhead that is designed to automatically shut to prevent oil leaks in the event of an accident.  Attempts to manually close the blowout preventer have not been successful.

The other containment options being explored are drilling a separate well nearby to plug the flow at a location below the blowout preventer and building underwater domes that would contain the oil until it could be safely pumped to the surface for disposal.  Both of these alternatives are being actively worked and will take months to complete.  It is estimated that 4.2 million gallons of oil will be released if the blowout preventer is not able to be closed.

The cause of the explosion is unknown at this time.  An investigation is underway by the Coast Guard and the Minerals Management Service.

A preliminary root cause analysis can be started using the information that is known and details can be added as they become available.  The analysis can be documented using a Cause Map which is a simple, intuitive format that visually lays out all known causes for an incident.  The first step in building a Cause Map is to determine how the organizational goals were impacted by the incident.  Causes for each impacted goal are determined to begin building the Cause Map.

In this case, the safety goal was impacted because 11 people were killed and several injured.  The environmental goal was impacted because there was a significant oil release.  The materials goal was impacted because the $700 million oil rig is a complete loss and the production/schedule goal was impacted because the oil drilling operation is shut down.

Click on the “Download PDF” button above to view an initial Cause Map.