How did the oil rig explode?

Answer 1

The Deepwater Horizon rig caught fire due to the uncontrollable flow of hydrocarbons (blow out) to the rig floor. There were a number of explosions on the rig, with the first explosions coming from the engine room, as the engines went out of control (reved at a high speed). Later explosions were most likely the result of large supplies of fuel onboard the rig.

The rig ultimately sank as a result of the fire and explosions. The causes continue to be investigated. However, one critical factor for the blow out is likely to be the foamed cement used to cement in the final casing. Laboratory analysis has shown the cement formulation was unstable in some of the tests. Another factor is the failure of blow out preventers to close.

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Answer 2

well there was pressure in the pipe which made it blow up.