BP Feared Spill of 3.4 Million Gallons a Day

NEW ORLEANS (AP) — On the day the Deepwater Horizon sank, BP officials warned in internal e-mails that if the well was not protected by the blowout preventer, crude oil could burst into the Gulf of Mexico at a rate of 3.4 million gallons a day — an amount a million gallons more than what the government later said it believed had spilled daily from the site.

The e-mail conversation, which BP agreed to release on Friday as part of federal court proceedings, suggests that BP managers recognized the potential of the disaster in its early hours, and that company officials sought to make sure that its model-developed information was not shared with outsiders.

The e-mails also suggest that BP was having heated discussions with the Coast Guard over the potential of the oil spill.

The messages were released as part of the court proceedings to determine the division of responsibility for the nation's worst offshore oil disaster, which began when the BP-leased Deepwater Horizon exploded on April 20, 2010, killing 11 men about 50 miles southeast of the Louisiana coast.

The first phase of the trial is scheduled to start on Feb. 27.

BP officials declined to comment on the e-mails.

The amount of oil that flowed from the well was officially calculated at 206 million gallons from at least April 22 until the well was capped on July 15, 2010. That is a daily flow rate of about 2.4 million gallons — two-thirds of BP's projection of what could leak from the well if it were an "open hole." BP has disputed the government's estimates.

Having an accurate flow rate estimate is necessary to determine how much in civil and criminal penalties BP and other companies that drilled the well face under the Clean Water Act.

In the string of e-mails, a BP official urged that the flow-rate projections not be shared and referred to the "difficult discussions" the company was having at the time with the Coast Guard.

Gary Imm, a BP manager, told Rob Marshall, BP's subsea manager in the gulf, to tell the modeler doing the estimates "not to communicate to anyone on this."

"A number of people have been looking at this," Mr. Imm wrote in an e-mail. "We already have had difficult discussions with the U.S.C.G. on the numbers," he added, referring to the Coast Guard and flow estimates.

On April 23, 2010, the Coast Guard, relying on BP's remotely operated vehicles, said no oil was leaking from the well a mile under the sea. A day later, Rear Adm. Mary E. Landry of the Coast Guard said oil was leaking at a rate of about 42,000 gallons a day. The Coast Guard and BP did not divulge how they had arrived at that figure.

A version of this article appeared in print on January 29, 2012, on page A17 of the New York edition with the headline: BP Feared Spill of 3.4 Million Gallons a Day.