segunda-feira, 7 de junho de 2010
Rate of Oil Leak, Still Not Clear, Puts Doubt on BP
Staring day after day at images of oil billowing from an undersea well in the Gulf of Mexico, many Americans are struggling to make sense of the numbers.
On Monday, BP said a cap was capturing 11,000 barrels of oil a day from the well. The official government estimate of the flow rate is 12,000 to 19,000 barrels a day, which means the new device should be capturing the bulk of the oil.
But is it? With no consensus among experts on how much oil is pouring from the wellhead, it is difficult — if not impossible — to assess the containment cap’s effectiveness. BP has stopped trying to calculate a flow rate on its own, referring all questions on that subject to the government. The company’s liability will ultimately be determined in part by how many barrels of oil are spilled.
The immense undersea gusher of oil and gas, seen on live video feed, looks as big as it did last week, if not bigger, before the company sliced through the pipe known as a riser to install its new collection device.
At least one expert, Ira Leifer, who is part of a government team charged with estimating the flow rate, is convinced that the operation has made the leak worse, perhaps far worse than the 20 percent increase that government officials warned might occur when the riser was cut.
Dr. Leifer said in an interview on Monday that judging from the video, cutting the pipe might have led to a several-fold increase in the flow rate from the well.
“The well pipe clearly is fluxing way more than it did before,” said Dr. Leifer, a researcher at the University of California, Santa Barbara. “By way more, I don’t mean 20 percent, I mean multiple factors.”
Asked about the flow rate at a news conference at the White House on Monday, Adm. Thad W. Allen, the Coast Guard commander in charge of the federal response to the spill, said that as BP captured more of the oil, the government should be able to offer better estimates of the flow from the wellhead by tracking how much reaches the surface.
“That is the big unknown that we’re trying to hone in and get the exact numbers on,” Admiral Allen said. “And we’ll make those numbers known as we get them. We’re not trying to low-ball it or high-ball it. It is what it is.”
Speaking at a briefing in Houston on Monday, Kent Wells, a BP executive involved in the containment effort, declined to estimate the total flow and how much it might have increased. He said that video images from the wellhead showed a “curtain of oil” leaking from under the cap.
“How much that is, we’d all love to know,” Mr. Wells said. “It’s really difficult to tell.”
He said that more than 27,000 barrels of oil had been collected, and that engineers were working to optimize the collection rate.
On Sunday, engineers halted their efforts to close all four vents on the capping device, because even with one vent closed, the amount of oil being captured was approaching 15,000 barrels a day, the processing capacity of the collection ship at the surface.
Mr. Wells reiterated that a second collection system, involving hoses at the wellhead, would be implemented “by the middle of June.” That oil would be collected by another rig with the ability to handle at least 5,000 barrels a day, he said.
The success of the containment device has cast new doubts on the official estimates of the flow rate, developed by a government-appointed team called the Flow Rate Technical Group. Before the riser pipe was cut, the group made estimates by several methods, including an analysis of video footage, and the overlap of those estimates produced the range of 12,000 to 19,000 barrels a day that the team reported on May 27. That was two to four times as high as the government’s previous estimate of 5,000 barrels a day, a number that had been widely ridiculed by scientists and advocacy groups.
Yet the scientists who produced that new range emphasized its uncertainty when they presented it. In fact, a subgroup that analyzed the plume emerging at the wellhead could offer no upper bound for its flow estimate, and could come up with only a rough idea of the lower bound, which it pegged at 12,000 to 25,000 barrels a day.
Fonte: New York Times (www.nyt.com)
Esse assunto foi tema de uma das perguntas do concurso do Banco do Brasil, promovido pela Fundação Getúlio Vargas ontem (domingo, 6/6).
Engraçado como o NYT se refere às suas fontes usando Mr., não é? Estamos tão acostumados aqui no Brasil a não usar pronomes de tratamento nas matérias...