BP oil company has begun pumping heavy mud into a blown-out well in the Gulf of Mexico in an effort to seal it off permanently. In Miami, The first phase of the operation could take as long as three days.
Engineers launched the so-called static kill operation on Tuesday, in the hopes of finally sealing the well that blew out more than 100 days ago.
BP officials say the static kill is the first step in a two-part operation that involves filling the well pipe with cement to block the release of oil and natural gas.
Crews are slowly pumping heavy drilling mud into a cap on the top of the well, to push down hydrocarbons that are already present in the well pipe. Teams must be careful that the mud does not raise pressure too high and cause possible damage to the well pipe.
BP senior vice president Kent Wells said engineers are proceeding cautiously with the static kill over the coming days.
"We just need to follow it as it goes," said Kent Wells. "That is why we indicated it is something in the range of a bunch of hours to a couple of days. It's really difficult to nail down, we are so early in the process. There is no way to give any early indication."
Wells said engineers may decide to finish the static kill operation by pumping cement into the top of the well. If not, crews will wait until the completion of a 5,500-meter relief well that will intersect the base of the well pipe.
The relief well will enable crews to conduct the second part of the kill operation, which involves pumping mud and cement into the bottom of the well.
BP's Kent Wells said engineers are focussing on the first phase - the static kill - to decide how to proceed.
"Based on how everything goes, that is when we will make the decision on what is the best way for us to continue to kill and cement this well," he said.
BP's Macondo well spewed oil and natural gas for nearly three months, before crews installed a cap that halted the leak last month.
U.S. scientists estimate nearly 5 million barrels of oil leaked from the damaged well, making it the largest accidental release of oil into the seas in history. A similar blowout off the coast of Mexico released 3 million barrels in 1979.
BP has set aside a $20-billion fund to assist fishermen and other Gulf coast businesses affected by the oil leak. So far, BP says it has paid more than $4 billion for clean-up efforts and claims payments.