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Scientists: Gulf spill is worldâ€™s largest accidental spill

03 August 2010 22:33 (UTC +04:00)

Baku-APA. As BP plans today to begin permanently plugging its Macondo well, new U.S. estimates say the Gulf spill is the worldâ€™s largest accidental release of oil ever into marine waters, APA reports quoting USA Today.
Federal scientists announced late Monday that the BP-managed well released 205.8 million gallons of oil (or 4.9 million barrels) into the Gulf of Mexico, which is far more than initial U.S. government or BP estimates.
These numbers also far outstrip estimates for what has ranked as the worldâ€™s largest unintentional spill -- Mexicoâ€™s Ixtoc I, which gushed 138 million gallons into the Bay of Campeche in 1979. Larger amounts of oil were intentionally spilled in 1991 during the Persian Gulf War.
The Macondo well gushed between 53,000 and 62,000 barrels a day from April 20 until it was capped July 15, according to scientists in the Flow Rate Technical Group, which is supervised by the U.S. Geological Survey and the U.S. Department of Energy. The scientists say their current estimates are accurate to within 10%.
BP, which captured about 800,000 of the 4.9 million spilled barrels through containment efforts, plans to do a preliminary test today before it begins to plug the well.
This "injectivity test" aims to figure out whether pumping heavy mud can effectively force oil down the well into the reservoir. BP planned to do the test Monday, but it found a "small hydraulic" leak in the capping stack that it had to fix first.
"This is a really positive step forward," Retired Coast Guard Adm. Thad Allen, the governmentâ€™s point man on the spill response, told reporters Tuesday at a news briefing in Houston. "Itâ€™s going to be good news in a time where that hasnâ€™t been very much good news, but it shouldnâ€™t be a cause for premature celebration," Allen said.
"Weâ€™re not anticipating" a problem with the "injectivity" test, BP senior vice president Kent Wells told reporters Monday in a technical briefing. He said he expected the "static kill," in which mud is poured into the well to push the oil down into its reservoir, to start shortly after the test and take a couple of days.
Wells said the "static kill" has a better chance of succeeding than did BPâ€™s failed "top kill" attempt in May, because the well is now capped so the mud can no longer escape out the top.
Still, Allen said Tuesday, "the static kill is not the end-all, be-all" for killing the well. He said the relief wells, which BP began drilling in May, will be needed to cement the well from the bottom, in a procedure known as the "bottom kill."
Well said the primary relief well, which BP began drilling May 2, is now only about 100 feet vertically and four feet laterally from its target and could reach it by Aug. 11. The energy giant began drilling a second, back-up relief well May 16.
Wells said he expects the "static kill" to require about 2,000 barrels of mud, but BP has 8,000 barrels ready on its Blue Dolphin vessel and another 20,000 barrels on its HOS Centerline. The heavy mud is routed from these surface vessels to another ship, the Q4000, which then pumps it into the wellâ€™s blowout preventer that sits just below its 75-ton cap.