BP engineers and the U.S. government’s science team met Monday afternoon to figure out the best way to relieve pressure in the outer shell of the Macondo well before BP is allowed to complete the relief well, the ultimate step in permanently sealing the exploded oil well in the Gulf of Mexico.
Although BP pumped cement into the well through a procedure called a “static kill” this month, the government wants the company to proceed with filling the well with cement through a relief well to make sure the broken well really is dead.
But now officials are concerned that pumping cement through the relief well could put too much pressure on the sealed outer layer of the well, called the annulus, and National Incident Commander Thad Allen asked BP to figure out how to relieve the pressure before he would let the company complete the relief well.
On Monday afternoon, advisers to BP and the federal government met to consider two options for handling the pressure, and they will advise Energy Secretary Steve Chu and Interior Secretary Ken Salazar, Allen said.
Chu will make a recommendation on how to proceed.
“We want to make sure before I give the order to intercept that we understand the implications of that pressure and how we will deal with it,” Allen said.
One option is to remove the existing capping stack and blowout preventer and put a new blowout preventer in its place. Taking anything off the well is considered somewhat risky, but a new blowout preventer would be best equipped to handle pressure and would enable officials to shut down the well if a problem arises.
If the scientists opt to remove existing equipment and install a new blowout preventer, BP would use the blowout preventer from the backup relief well that has been drilled. BP would have to get permission from the Bureau of Ocean Energy Management, the successor to the Minerals Management Service, to temporarily abandon the well with a cement plug so it could take off the blowout preventer.
The other option is to develop a pressure relief mechanism in the capping stack. That would keep more of the existing structure in place, but it would take more time because engineers would have to design a new piece of equipment and have it fabricated.
Allen said Monday that the government and BP will decide “in the next day or two” how to proceed.
Considerations about how to handle pressure in the outer portion of the well will likely push back the ultimate shutting down of the Macondo well until at least next week.
The move also sidesteps considerations of the remnants of Tropical Depression 5, which the National Hurricane Center on Monday gave a 60 percent of re-forming into a tropical system. On Monday afternoon, the site where the Deepwater Horizon rig sank on April 20 was experiencing 8-foot waves.
Once Allen allows BP to resume drilling, it should take 96 hours for the company to drill the final length and intercept the well. As with the “static kill,” it will take 24 to 36 hours to pump cement into the well and permanently kill it.
But, Allen said, that five- or six-day period won’t begin until BP has made whatever changes are needed to deal with the pressure.
“We’re being responsible in how we’re moving forward,” Allen said. “We have to have a stake in the heart of this well.”