Tuesday, May 25, 2010

BP engineers prepare 'top kill' attempt to stop oil flow into the Gulf


By Joel Achenbach and Steven Mufson
Washington Post Staff Writer

The most critical moment in the oil spill crisis in the Gulf of Mexico is at hand, as BP engineers armed with 50,000 pounds of dense mud and a fleet of robotic submarines are poised to attempt a "top kill" maneuver to plug the leaking well a mile below the surface.

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This will be the first attempt to stop outright the flow of oil that has created a vast slick in the gulf and is now coming ashore and into marshes in Louisiana. Previous efforts by BP since the April 20 blowout on the Deepwater Horizon drilling rig have focused on containing and/or dispersing the oil coming from a collapsed pipe. Those efforts have had limited success.

Now the equipment for the top kill is in place at the sea bottom and engineers are beginning a set of diagnostic tests on the five-story-tall blowout preventer that sits atop the wellhead. By probing conditions inside the blowout preventer, BP will learn how much pressure must be overcome when the drilling mud is injected into the well.

"We've got a crack team of experts that are going to pore over the diagnostic data," BP's senior vice president of exploration and production, Kent Wells, told reporters in a conference call Tuesday morning. "There is a remote possibility that we would get some information that it wouldn't work."

After the tests are complete, the final decisions will be made on precisely how to proceed. There are five portals into the blowout preventer. Mud will be pumped at 40 barrels a minute, or some similar quantity, through multiple lines, driven by a 30,000-horsepower engine on a ship at the surface some 5,000 feet above the well. Some of that mud will not go down into the well but will leak out the end of the damaged pipe, but the engineers have factored that into the calculations, Wells said.

"We know we'll lose some out the top, but can we pump fast enough to ultimately kill the well?" Wells said. He said the goal is to "outrun the well."

This could work, but it's a challenging environment, said Tadeusz Patzek, chairman of petroleum engineering and geophysics department at the University of Texas at Austin: "They need to get access to the well. They were just working on finding ways through the choke and kill lines and figuring out how to do that safely. Remember that they are one mile in pitch-black water."

The exact timing and pace of the maneuver has not been set, but Wells said the mud injection would begin no sooner than Wednesday and he cautioned that it could take as much as two days to complete.

He also gave details for the first time of yet another backup plan if the top kill doesn't work. This would involve what BP calls the LMRP cap, for Lower Marine Riser Package. The very top of the blowout preventer would be severed using the robotic submarines. This would temporarily increase the flow of oil by 5 to 15 percent, Wells estimated. But then a new containment dome would be lowered onto the blowout preventer and would capture much more of the oil than has been captured so far.

He said the team, which includes experts from other oil companies as well as government engineers, has been devising the top kill procedure since the very beginning of the crisis.

"It has been done successfully in the past but it hasn't been done at this depth," Wells said.

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