BP prepares complex 'top kill' bid to plug well

The blowout preventer had been meant to be used as a last resort to control oil flow. It failed for yet unknown reasons.

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After the late April collapse of the Deepwater Horizon oil rig, which had been floating one mile above the wellhead, the pipe connecting the rig to the wellhead was bent out of shape and began spewing oil into the water. There were two leaks in the pipe and one at the wellhead.

Several attempts to contain oil have been made on the pipes, with varying degrees of success. Attempts to cover one leak with a large metal canopy that would redirect oil into a waiting container ship above failed after crystals materialized in the canopy, preventing a proper flow of oil. A later attempt to insert a tube into one of the pipes was partially successful, but only captured about 20 percent of the oil flowing out.

The top kill attempt involves reactivating control lines feeding into the wellhead through temporary high-pressure hoses that will be used to pump drilling mud into the well, according to Lars Herbst, a regional official with the U.S. Minerals Management Service.

His agency has been working closely with BP staff to "ensure that procedures are conducted in a safe, environmentally sensitive manner and reduce any risk of additional impact," he told reporters in a conference call on Thursday.

He said the procedure was a "critical and very complex operation" where his staff had been providing technical assistance for some time.

In response to a reporter's question asking if there was a possibility that such a procedure could make things worse, BP Chief Operating Officer Dough Suttles said that the top kill procedure had not been previously attempted because diagnostic information needed to be obtained about the condition of the blowout preventer. Other tests were being finalized

"It takes considerable planning to actually pull off an operation of this scale. Most of the big equipment has actually been mobilized and is either on-scene or en route," he said on Thursday.

The fluid, which is much heavier than oil or water will be forced through the blowout preventer at high pressureby way of two or three inch holes known as "choke and kill lines," Suttles had said earlier last week.

At some point that would stop the flow of oil, opening the opportunity for cementing the well shut by pumping in cement. 

Mary E. Landry, a Rear Admiral with the U.S. Coast Guard who has been helping to coordinate broader efforts beyond stopping the spill says those working together on the response are "anxious" to see the top kill procedure work, but added that people are mobilized for long term response efforts in case it fails. A permanent solution is expected to be reached in August, when a pair of relief wells, 13,000 feet below the sea floor, have been bored to divert the flow of oil from the current leak.

"[W]e absolutely are holding out hope that top kill works," she said. "But we also have the plans in place that say, if it doesn't work, you know, we have to be ready for the long haul to see this through."

Clarification: A clarification was added to an article from May 22, 2010, indicating that drilling mud would be pumped down into the well at high pressure with the aim of stopping the flow of oil and gas, and opening way for cementing it.

On the Web:

Link to BP video of underwater "Top Kill" preparations. Click here.