BP Explains the Deepwater explosion

BP today released its version the events that led up to the April 20 explosion and fire. There are other theories to come:

The explosion that sank the drilling rig came less than a day after workers finished pumping concrete into the well, a step toward closing it off temporarily. BP planned to return to the well later to set up a permanent rig and start producing oil.

Encasing a newly drilled well in concrete is a critical step in developing the well, and it presents many risks.

The concrete involved is highly specialized. It needs to be blended and stirred properly. It also must be pumped down into the well so that it comes out the bottom and oozes back up around the well casing, forming a tight seal.

The concrete work apparently did not achieve a complete seal, and natural gas started seeping into the well in the late stages, the lawyers said. But idling a rig to address such a problem can cost huge sums. The lawyers said that supervisors either missed or ignored the signals and proceeded with the job.

When workers released the last valves that were holding back the natural gas that had built up inside the well, the gas shot up the pipe and sprayed into the drilling rig, igniting the fireball that caused the deaths of 11 workers, injured others and sank the rig, the lawyers said.