BP says spill flow lower than government estimate: panel

Oil gushes from BP's ruptured well in the Gulf of Mexico, in this frame grab captured from a BP live video feed on July 11, 2010.

WASHINGTON (Reuters) - BP Plc believes the actual flow rate of its massive oil spill in the Gulf of Mexico may have been significantly less than the government's final estimate, according to comments released by the White House oil spill commission on Friday.

The government has said BP's ruptured undersea well released between 53,400 and 60,000 barrels per day, but commission staff said BP orally told them those estimates were 20 percent to 50 percent too high.

"They rely on incomplete or inaccurate information, rest in large part on assumptions that have not been validated, and are subject to far greater uncertainties than have been acknowledged," BP said in written comments submitted to the commission in October.

The disagreement over the amount of oil that flowed from BP's ruptured undersea well sets up a legal battle over the billions in dollars in government fines the oil giant faces relating to the accident.

A lower flow rate would call into question the government's estimates that BP's Macondo well spewed a total of 4.9 million barrels of oil this summer and would impact the amount of fines BP would have to pay for the drilling disaster.

Under the Clean Water Act, the government could fine BP up to $4,300 for each barrel of oil spilled into the Gulf, which would mean a maximum fine of $21.1 billion for the oil giant, based on the government's spill estimates.

"The relevance of how much oil was released obviously plays into the calculation of fines," said Commissioner Terry Garcia. "It's not surprising they think it was lower."

In its comments, BP said the government's estimates seemed to be biased toward the maximum amount of oil that could have been discharged instead of the amount most likely to have been released.

BP said more information, such as an analysis of the rig's blowout preventer, was needed before it can develop its own estimate of the well flow rates. But, ultimately, the company said, a full review will show "possibly far less oil" was spilled than the government estimated.

The issue of flow rates is "very complicated because it involves the flow path during different times in the spill ... it's going to be litigated," Priya Aiyar, deputy chief counsel of the commission, said at a meeting on Friday.

The comments came as the commission weighed proposals that would call for requirements for more accurate flow rate estimates from the start of a major oil spill.

Some commissioners said they believed the government should be responsible for independently measuring flow rates, and not be reliant on the companies responsible for spills.

Lack of accurate flow rate estimates at the start of the BP spill in April eroded public confidence in the government's ability to handle the accident response, the panel said.

Charged with guiding the future of offshore drilling, the commission is working to develop policy recommendations to prevent or better respond to spills.

The seven-member panel's official report is set to be released on January 11, but it will be up to the Obama administration, lawmakers and the oil industry to decide whether to implement whatever framework the panel lays out.

(Editing by Walter Bagley)