BP WANTS a US federal judge to rule that an estimated 800,000 barrels of oil collected at the head of its runaway undersea Gulf of Mexico well in 2010 should not be counted in determining the company's civil fine for Clean Water Act violations.
Such a ruling could reduce BP's fine by as much as $US3.4 billion ($A3.2 billion) if the company is found to have acted with gross negligence when its Macondo well blew out off the Louisiana coast, leading to the worst offshore oil spill in US history. Eleven rig workers were killed when the Deepwater Horizon drilling rig, which BP had been leasing from Transocean, exploded.
The US government has asserted that the well discharged 4.9 million barrels of oil. BP stated again in its filing on Friday that it believes the spill was significantly smaller, though it hasn't publicly provided its own estimate.
With a finding of gross negligence, the 4.9-million-barrel figure would carry a maximum Clean Water Act fine of more than $US21 billion.
The law allows for a fine based simply on the amount of oil discharged. BP points out in its motion that some courts have interpreted the law to mean that oil has to be discharged into water or the environment to count.
Before it capped the well in July 2010, BP captured some of the gushing oil before it spilt into the water a mile below the Gulf surface. The government concluded in August 2010 that some 800,000 barrels of oil was collected at the wellhead, the assemblage of equipment that is attached to the opening of an oil or gas well.
US Interior Department officials have refused to say whether the government believes any of that oil touched the water before being collected. A US Justice Department spokesman declined to comment on BP's filing.
A civil trial on the tangle of spill-related litigation is set to begin on February 25.
The first phase of the trial will deal with apportioning blame among BP and the other companies. The second phase will deal with the amount of oil that spilt.