To clarify yesterdays questions: The "Deepwater Horizon" was a drilling platform... it was being prepared to move to another location so a pumping platform could come in and extract the oil.
The explosion was a result of trying to simplify and shorten the process of attaching the pumping platform. As they were sealing the pipe in order to move, they used seawater instead of 'drilling mud' to block the pipe while final disconnections were mead. Drilling mud would have taken a couple of weeks to 'clear', and delayed the start of pumping oil. There was a flawed seal which was not tested properly which allowed pressure to 'blow out' the seal and send high-pressure water & oil up and cause the explosion & fire.
It was partially greed & impatience and careless maintenance by BOTH BP and the operators that led to the failure, but there was a big argument in the hours before the fire as to how to do the sealing... **BP** overruled those doing the work and told them to use the shortcut....and then claimed "We aren't the operators."