Oil rig explosion caused by methane bubble?

I’m seeing reports this morning that documents from an internal investigation by BP show the oil rig explosion at the Deepwater Horizon site in the Gulf of Mexico might have been caused by a methane bubble that overwhelmed safety seals and exploded, igniting the oil.

Portions of the interviews, two written and one taped, were described in detail to an Associated Press reporter by Robert Bea, a University of California Berkeley engineering professor who serves on a National Academy of Engineering panel on oil pipeline safety and worked for BP PLC as a risk assessment consultant during the 1990s. He received them from industry friends seeking his expert opinion.

Workers set and then tested a cement seal at the bottom of the well. Then they reduced the pressure in the drill column and attempted to set a second seal below the sea floor. A chemical reaction caused by the setting cement created heat and a gas bubble which destroyed the seal.

The gas apparently shot up out of the drilling conduit and flooded an area of the rig that contained electrical sources that served as an ignition point, exploding and setting the oil afire. Read the story for details.

I scuba dive so the concepts of gas under pressure and various pressure effects are known to me. I find this explanation to be completely plausible. However, I want to be clear about something: the interviews described are, basically, “leaks” of information that wasn’t intended for publication. I have no real reason to doubt Robert Bea, the man who gave the information over to the AP reporter who filed the story, but I don’t really know him, either. I have no idea what motive he might have and I have seen nothing that corroborates his report. We’ll have to wait for that for a bit. The report, if true, raises the question of whether anything described about this incident is abnormal. By that I mean were any of the actions taken outside of accepted practice? Have these techniques been deployed successfully anywhere else and was there anything known about the site that might have called such techniques into question? Again, we don’t have that information yet.

I understand that the recovery system I described a few days ago has been deployed to the site and the “dome” device has been lowered into place. We should know by this afternoon whether the system is working as intended.

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2 comments

  1. Ric,
    This is very interesting. However, as one who has done a lot of work in degasification and intrinsically safe electrical and electronic equipment, I would think that all of the electrical equipment in an area where explosive gas mixtures might be found/occur would be either intrinsically safe or in explosion proof containments. Did someone leave a door or cover open while operations were occurring? That would be clearly negligence or at least lack of proper supervision/management. I guess time will tell.

  2. John, my understanding is that the enormous expansion broke through a variety of seals as it shot out the top, breaching a nearby room that’s not supposed to be in the path of any outgassing. In short, gas isn’t supposed to be able to get to that area. Of course you’re right that we still don’t know the whole story so there might be some of that negligent / improper supervision stuff involved.

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