What Caused the BP Rig to Explode? The Engineers Explain

A month after the initial incident, we are still trying to understand, not to mention stop, the environmental disaster that resulted from the explosion of the Deepwater Horizon, the submersible drilling rig that may lead to the utter devastation of the entire Gulf of Mexico region. ut the precise cause of the disaster has been enshrouded in excuses, corporate obfuscation, and political blustering. To clear up the issue, the folks at Oil Drum have consulted with a number of drilling and completion engineers and put together a plausible timeline of precisely what went down in Deepwater Horizon’s final hours. While it is a fact-based interpretation rather than a statement of absolutes, the chronology provides a heavily detailed picture, complete with charts and graphs. It begins with the following:

1. The well had reached a depth of 13,293 ft below the sea floor. The final string of production casing from the wellhead at the sea floor to total depth had been put in the hole, and cemented in place on April 19, 2010. 2. Only 51 barrels of cement were used according to the well plan. This was not sufficient to ensure a seal between the 7-inch production casing and the previously cemented 9 7/8-inch protection casing. 3. Mud had been lost to the reservoir while drilling the bottom portion of the well (this is called “lost circulation”). It usually indicates good reservoir quality, an interval of lower pressure or both, and can result in an enlarged wellbore or “washout”. The significance of this is that it might have been difficult to create a good cement seal between the casing and the formation…. 4. The cement contained a nitrogen additive to make it lighter so that it would flow more easily and better fill the area between the casing and the lost circulation-washout zone. This also may have decreased its sealing effectiveness. Gas from the reservoir may have further diluted the viscosity of the cement. 5. While waiting approximately 20 hours for the cement to dry on April 20, the crew began displacing the drilling fluid (“mud”) in the wellbore and riser with sea water before setting a cement plug and moving off location. This mud was pumped into tanks at the surface, and then onto a platform supply vessel alongside the rig.

Meanwhile at the New Yorker, environmental reporter Elizabeth Kolbert offers a more succinct explanation

:

In an immediate sense, the causes of the catastrophe are technical. Apparently, the Deepwater Horizon well was inadequately sealed, and natural gas built up inside it. When workers on the rig tried to activate the well’s blowout preventer, it failed. An attempt to activate the blowout preventer after the fact, using undersea robots, also proved unsuccessful. Another effort to cap the leak, by using what amounted to a hundred-ton steel funnel, flopped as well. Last week, BP finally succeeded in inserting a mile-long tube into the riser leading from the well. The company said that it was capturing a thousand barrels of oil a day, which is what it originally claimed that the well was leaking; nevertheless, crude continued to pour into the Gulf.

Granted, as Kolbert notes, the larger issue is that we are going to greater and greater lengths (and taking greater risks) to extract oil from the earth. The solution to which is another discussion entirely.