The oil rig explosion at the Gulf of Mexico was triggered by a bubble of methane gas that rose through the drill column and expanded.
As per interviews of rig workers, it then burst through several seals and barriers before exploding.
The blast on April 20th had killed 11 workers. Investigations are still on the cause of the explosion. There were two written and one taped interview done during the investigation by BP. Robert Bea, a University of California Berkeley engineering professor who serves on a National Academy of Engineering panel on oil pipeline safety had described portions of the interview in detail to a Associated Press reporter.
As per the transcripts, a group of BP executives were on board the Deepwater Horizon rig to celebrate the project’s safety records.Bea believes basis the interviews that workers had set and tested a cement seal at the bottom of the well. Later the pressure in the drill column was reduced attempts were made to set a second seal below the sea floor. Heat was generated by the setting cement due to a chemical reaction and then a gas bubble destroyed the seal.
Bea also said that the methane gas grew and intensified from the high pressure environment of deep seas to comparative lower pressure of lesser shallows and eventually broke through safety barriers.
On the rig the worker noticed that the sea water in the drill column started suddenly shooting back at the workers and rose 240 ft in the air. Soon the gas followed the water and later it was the oil that started to spill. “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 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.” As per the interview, a gas cloud covering the rig caused the engines to run too fast and subsequently explode.
BP spokesperson said, Clearly, what happened on the Deepwater Horizon was a tragic accident, BP executives were injured but all of them survived while nine crew on the rig floor and two died.
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BP had lowered a 100-ton concrete-and-steel vault onto the ruptured well on Friday. Post that underwater robots guided the 40 ft tall box into place. The workers will need12 hours for the contraception to settle on the sea floor. If all goes well then the box should capture 85% of the oil by Sunday.
Crews have been laying booms, spraying chemical dispersants and setting fire to the slick to try to keep the slicks from coming ashore. The uncertainty and risks still remain specially since such practices have never been tried before at such depths. A second box will be dropped in a an identical fashion if this box works well.
Sideways drilling into the well is also going on with the hope of plugging it up with mud and water while investigators have been focusing on the so called blow out preventor.
Well holes are blocked by piping and pumped-in materials like synthetic mud, cement and even sea water. Cement is used to plug the pipes so fluid and gas in unable to push up inside the pipe.