The deadly Deepwater Horizon blowout was triggered by a bubble of methane gas that shot up the drill column, expanding quickly as it burst through several seals and barriers before exploding, according to interviews with rig workers. "A small bubble becomes a really big bubble," says an expert privy to the interview transcripts. "So the expanding bubble becomes like a cannon shooting the gas into your face."
As the rig was being converted from an exploration well to a production well, workers set and tested a cement seal at the bottom of the well. Then they attempted to set a second seal. A chemical reaction caused by the setting cement created a gas bubble that destroyed the seal. Up on the rig, the first thing workers noticed was the sea water in the drill column suddenly shooting back at them, rocketing 240 feet in the air. Then, gas surfaced. Then oil. A gas cloud covered the rig, causing giant engines on the drill floor to run too fast and explode. The engines blew off the rig and set "everything on fire," the account said. Another explosion below blew more equipment overboard.