BP said Saturday it began removing drill pipe and other equipment from a damaged wellhead under the Gulf of Mexico, as it prepares to replace its giant blowout preventer valve with a new one.
Called a "fishing" procedure, the pipe removal was authorized late Friday by US spill response chief Thad Allen after a successful 48-hour "ambient pressure test" to ensure no oil will leak during the procedure, BP said.
Allen also gave BP until Sunday to submit a proposal for removing the blow out preventer that will not interfere with a federal investigation into the April 20 explosion that unleashed the worst oil spill in US history.
A so-called "bottom kill" operation to permanently seal the ruptured well has been delayed until the blow out preventer is replaced.
The bottom kill involves intercepting the crippled well with a relief well, which then pumps heavy drilling oil and cement into the oil well to permanently plug it.
Originally scheduled for mid-August, the bottom kill was postponed earlier this week to at least the second week of September because of concerns about pressure at the drill site.
The ruptured Macondo well was capped on July 15 and earlier this month BP engineers performed a "static kill" which plugged it with heavy drilling fluid and then sealed it with cement.
However, there is an area between the well and the outer well bore called the annulus which must still be sealed off from the reservoir miles below the surface of the Gulf of Mexico.
Engineers are worried that on removing the blow out preventer, the pressure behind the annulus could increase too quickly and compromise the cement plug above it.
In reference to the delicate blow out preventer removal, Allen told BP "the procedure may not be commenced without my prior approval."
He also ordered BP to provide "continuous live," remote video coverage of the operation, as well as "unfettered access" to federal investigators to observe and record the entire process.
Allen said the Joint Investigation Team he heads "will take custody of all equipment removed from or associated with the BOP (blow out preventer) stack... from the time it is removed from the well head and will maintain that custody throughout the lifting process."
Explore further: Pact with devil? California farmers use oil firms' water