The raising of the BOP from the Macondo Well is not just a safety precaution. The BOP is also evidence that may reveal how the Gulf oil spill happened.
The 450 ton BOP resting a mile below the surface of the Gulf of Mexico is set to become Exhibit A in a Justice Department investigation into what caused the explosion aboard the Deepwater Horizon rig, killing 11 men, sinking the platform, and resulting in the biggest oil spill in U.S. history. Why the “shear ram” valve failed to slice through the drill pipe shutting off the well after the explosion on April 20th may finally be known.
Thad Allen, gave BP and Transocean, the drill rig operator, permission to replace the Deepwater Horizon’s BOP with another and to bring the failed unit to the surface. The BOP will hopefully provide clues at to whether the blowout was a result of human error, mechanical failure, bad maintenance, faulty procedures — or a combination of those.
On example that’s been raised is: “the question of whether the BOP was opened and closed multiple times in the confusion of the blowout after high-pressure gas started shooting across the deck of the Deepwater Horizon rig. That might explain why, in video images, two pieces of pipe appeared to be sticking out of the top of the BOP. If the unit makes it to the surface with the pipe still inside it, part of the mystery could be solved.”
“The BOP could have closed, once shut off at the sea floor,” he explains. “But with all the expanding oil and gas still flowing to the surface a mile above, there could have been confusion aboard the rig over whether it actually closed or not – and the operators might have tried it again.”
Dan Albers, a petroleum engineer and member of the Deepwater Horizon Study Group at UC Berkeley, says the BOP could help answer questions about a major theory concerning the device’s malfunction.
If oil and gas shot up the gap, or “annulus,” between the rock and the drill casing (a steel pipe just over nine inches wide), it could have lifted that large-diameter pipe and jammed it up into the vicinity of the BOP shear rams. BP never installed the casing hanger lockdown device, Mr. Albers says. If that happened, it would have made it impossible for the blind rams to close.
Under the plan to replace the BOP, BP has been directed to flush out the current blowout preventer and capping stack, clean it, and fill it with sea water. After that would come pressure tests. If those tests show the cement cap is holding, then the BOP could be removed and replaced by another BOP now being used by the second relief well from the Development Driller II rig.
The main reason for doing this, Allen said, is to put the best possible BOP on the well in advance of pumping heavy mud into the bottom of BP’s Macondo well through the adjacent primary relief well. It’s a safeguard just in case any weaknesses remain in the concrete cap already put in place from the top last month.