BP began a "static kill" operation of its blown-out Gulf of Mexico well on Tuesday, the first step of a two-punch strategy to permanently plug the world's worst accidental marine oil spill.
The operation, which will pump heavy drilling mud and later cement into the well shaft, is the next move to definitively subdue the unstable deepwater gusher that was provisionally capped in mid-July.
The "static kill" would take 33-61 hours to complete, officials said.
"The aim of these procedures is to assist with the strategy to kill and isolate the well, and will complement the upcoming relief well operation," BP said.
A relief well to complete the permanent sealing of the Macondo well should be finished later in August, depending on weather conditions.
The full magnitude of the Gulf of Mexico spill, triggered in April by a deadly rig explosion at the BP-owned Macondo well, became apparent on Monday as government scientists released revised figures showing almost 5 million barrels of oil leaked before the well was temporarily capped on July 15th.
This made it the world's largest accidental release of oil, surpassing the 1979 Ixtoc well blowout in Mexico's Bay of Campeche that gushed almost 3 million barrels.
Retired Coast Guard Admiral Thad Allen, who oversees the US oil spill response, said engineers had succeeded in halting a hydraulic leak found on Monday in the cap that could have hindered the "static kill" operation to pump drilling mud, and possibly later cement, into the top of the well.
Adm Allen said engineers were moving cautiously so as not to damage the fractured well and cause fresh leaks. "We don't know the exact condition of the well," he said.
The "static kill" will be the first step of a two-pronged strategy that will aim to finally seal the Macondo deposit with more mud and cement injected through relief wells that will deliver a definitive "bottom kill."
"This thing won't be truly sealed until those relief wells are done," Adm Allen said.
The spill, already the worst in US history, has unleashed an environmental and economic catastrophe on the Gulf Coast, disrupting the livelihoods of fishermen and tourism operators and triggering a barrage of damages lawsuits against BP.
The company has said it will pay all legitimate claims and clean up fouled beaches and marshes.
Reuters