If the drill pipe being used to recover some of the oil is anchored in any way to the riser, it should be filled with heavy mud to assist in the top kill procedure, even could continue to pump mud to some extent for the duration of kill.
"Reporting from Houma, La.Engineers have succeeded in stopping the flow of oil and gas into the Gulf of Mexico from a gushing BP well, the federal government's top oil spill commander, U.S. Coast Guard Adm. Thad Allen, said Thursday morning.
The "top kill" effort, launched Wednesday afternoon by industry and government engineers, has pumped enough drilling fluid to block all oil and gas from the well, Allen said. The pressure from the well is very low, but persists, he said.
Once engineers have reduced the well pressure to zero, they will begin to pump cement into the hole to entomb the well. To help that effort, he said, engineers are also pumping some debris into the blowout preventer at the top of the well."