BP takes tests before 'bottom kill'

US government's BP oil spill incident commander Thad Allen

Source: Press TV
http://www.presstv.ir/detail.aspx?id=138731&sectionid=3510203

The US has ordered BP to run a series of tests before completing a relief well to permanently seal the runaway Gulf of Mexico Horizon oil well with a "bottom kill."

The delayed drilling of the relief well's last 30 meters and the final capping procedure are to finish in a few days once the operation gets the green light from the US government's oil spill commander Thad Allen.

After a series of setbacks, BP was able to stop the gush of oil into the sea on July 15 with a temporary cap. The ruptured well was blocked with cement on August 5 and tests were conducted on the integrity of the plug.

In a Saturday statement, Allen said that considering "the results of the post cement pressure test, and in response to BP's request to consider foregoing the relief well," the "bottom kill" operation could go ahead.

"The Government Scientific Technical Team has determined that the benefits of the bottom kill procedure outweigh the risks," AFP quoted the retired US Coast Guard admiral as saying.

However, before the drilling of the relief well can resume, Allen asked BP to present plans for a "pressure relief system ... including any necessary containment option," in case excessive pressure might accumulate at the well head.

He also demanded a series of pressure tests "to assess the stability of the well" when the current damaged well stack is replaced with a new one.

Before the stack is removed, Allen said he wants BP to prove that the annulus between the well pipe and the outer well bore is either leak resistant, or provide a proper risk assessment of a possible leak.

About 1,000 barrels of oil are believed to be trapped in the well's annulus and it is possible that some of the cement pumped in from above effectively closed the annulus from the surface. A decision was made nonetheless for the bottom kill operation to continue and cement be pumped all the way to the well's source under the Gulf of Mexico.

The well ruptured when the BP-leased Deepwater Horizon rig sank on April 22 following a massive explosion that killed 11 workers, letting 4.9 million barrels of oil into the Gulf of Mexico -- the biggest maritime oil spill disaster of all time.