By Chris Baltimore
HOUSTON (Reuters) - U.S. scientists on Thursday doubled their high-end estimate of the amount of crude oil flowing from BP Plc's stricken Gulf of Mexico well.
They said between 20,000 and 40,000 barrels (840,000 and 1.7 million gallons/3.2 million and 6.4 million liters) of oil flowed from the well before June 3, when BP's remotely operated robots sawed through an underwater pipe to clear the way for a capping procedure.
The cutting of the pipe likely increased the flow, but BP says it has collected 73,324 barrels (3.1 million gallons/11,7 million liters) of oil since installing the capping system.
Even at the minimum estimated rate of 20,000 bpd, the well has dumped just over a million barrels of oil into the Gulf of Mexico since the Deepwater Horizon rig exploded on April 20 -- more than four times the amount that the Exxon Valdez spilled into Prince William Sound in Alaska in 1989.
The new estimates were made by the so-called Flow Rate Technical Group and announced by U.S. Geological Survey Director Marcia McNutt. BP had no input into the team's findings.
The well's average daily rate was 25,000-30,000 barrels, according to the group's findings.
The new figures are considerably higher than the prior "best estimate" of 12,000-19,000 bpd issued by the flow rate group on May 27.
Estimates have steadily climbed from the 5,000 bpd level initially cited by U.S. and BP officials, though BP had said that such estimates were unreliable.
One estimate, by researchers at Woods Hole Oceanographic Institution, would imply a flow rate of 50,000 bpd, McNutt said.
"You probably get to about 50,000 if you make some assumptions that they weren't quite willing to make," McNutt said.
The wide variation in the figures points to the difficulty in estimating flow of a well that is 1 mile beneath the surface and reachable only by remotely operated robots.
McNutt admitted the estimate was "still a work in progress" and that the numbers were "all over the board."
"There is a significant difference between the lowest possible estimate and the highest possible estimate," which the team will try to resolve in future studies, McNutt said.
Scientists have not estimated the flow since BP sawed through the riser pipe a week ago. U.S. Interior Secretary Ken Salazar told a congressional panel on Wednesday that the cut may have increased the rate by 4 to 5 percent.
(Additional Reporting by Kristen Hays; editing by Mohammad Zargham)