Worth reading: An excellent possible explanation for the Gulf oil rig blowout
Here is an analysis, in layman's terms, based on interviews with survivors of the disaster that 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.
In it, we discover that "A group of BP executives were on board the Deepwater Horizon rig celebrating the project's safety record, according to the transcripts. Meanwhile, far below, the rig was being converted from an exploration well to a production well."
The possible cause was a methane bubble that exploded up drill column, setting off a series of disastrous explosions.