BP at the weekend lowered a 40-foot-tall (12 meter) steel chamber over the oil leak about a mile below the surface, hoping to capture the 5,000 barrels of crude oil leaking each day and pump it to a ship. The effort failed when an icy mixture of gas and water near the seafloor clogged the chamber, forcing the company to remove it and study how to stop the ice forming before trying again.

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.

Based on the interviews, Bea believes that the 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.

Deep beneath the seafloor, methane is in a slushy, crystalline form. Deep sea oil drillers often encounter pockets of methane crystals as they dig into the earth.

As the bubble rose up the drill column from the high-pressure environs of the deep to the less pressurized shallows, it intensified and grew, breaking through various safety barriers, Bea said.

"A small bubble becomes a really big bubble," Bea said. "So the expanding bubble becomes like a cannon shooting the gas into your face."

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, he said. Then, gas surfaced. Then oil.

"What we had learned when I worked as a drill rig laborer was swoosh, boom, run," Bea said. "The swoosh is the gas, boom is the explosion and run is what you better be doing."

The gas flooded into an adjoining room with exposed ignition sources, he said.

"That's where the first explosion happened," said Bea, who worked for Shell Oil in the 1960s during the last big northern Gulf of Mexico oil well blowout. "The mud room was next to the quarters where the party was. Then there was a series of explosions that subsequently ignited the oil that was coming from below."

BP’s containment system, now set aside on the seabed, was the London-based company’s plan to slow the spread of oil while it drills a so-called relief well to inject heavy mud and cement into the leak to plug it permanently. BP said it may try to jam the well by injecting pieces of rubber and installing a blowout preventer to shut off the flow.

The company is preparing a second, smaller containment dome to be lowered over the main leak. It is designed to resist the formation of large hydrate volumes, the company said in a statement. BP will also try to contain the leak using a “top kill” option after working on the well’s blowout preventer.