Gulf Spill May Far Exceed Official Estimates
Oil leaks into the Gulf of Mexico from the end of the pipe - Oil leaks into the Gulf of Mexico from the end of the pipe that was supposed to pump oil from the sea floor before the Deepwater Horizon oil rig exploded and sunk last month. (BP PLC / AP)
The amount of oil spilling into the Gulf of Mexico may be at least 10 times the size of official estimates, according to an exclusive analysis conducted for NPR.
At NPR's request, experts examined video that BP released Wednesday. Their findings suggest the BP spill is already far larger than the 1989 Exxon Valdez accident in Alaska, which spilled at least 250,000 barrels of oil.
BP has said repeatedly that there is no reliable way to measure the oil spill in the Gulf of Mexico by looking at the oil gushing out of the pipe. But scientists say there are actually many proven techniques for doing just that.
(John Moore / Getty Images)
Steven Wereley, an associate professor of mechanical engineering at Purdue University, analyzed videotape of the seafloor gusher using a technique called particle image velocimetry.
A computer program simply tracks particles and calculates how fast they are moving. Wereley put the BP video of the gusher into his computer. He made a few simple calculations and came up with an astonishing value for the rate of the oil spill: 70,000 barrels a day -- much higher than the official estimate of 5,000 barrels a day.
The method is accurate to a degree of plus or minus 20 percent.
Given that uncertainty, the amount of material spewing from the pipe could range from 56,000 barrels to 84,000 barrels a day. It is important to note that it's not all oil. The short video BP released starts out with a shot of methane, but at the end it seems to be mostly oil.
"There's potentially some fluctuation back and forth between methane and oil," Wereley said.
But assuming that the lion's share of the material coming out of the pipe is oil, Wereley's calculations show that the official estimates are too low.
"We're talking more than a factor-of-10 difference between what I calculate and the number that's being thrown around," he said.
At least two other calculations support him.
Timothy Crone, an associate research scientist at the Lamont-Doherty Earth Observatory, used another well-accepted method to calculate fluid flows. Crone arrived at a similar figure, but he said he'd like better video from BP before drawing a firm conclusion.
Eugene Chiang, a professor of astrophysics at the University of California, Berkeley, also got a similar answer, using just pencil and paper.
Without even having a sense of scale from the BP video, he correctly deduced that the diameter of the pipe was about 20 inches. And though his calculation is less precise than Wereley's, it is in the same ballpark.
"I would peg it at around 20,000 to 100,000 barrels per day," he said.
Chiang called the current estimate of 5,000 barrels a day "almost certainly incorrect."
Given this flow rate, it seems this is a spill of unprecedented proportions in U.S. waters.
"It would just take a few days, at most a week, for it to exceed the Exxon Valdez's record," Chiang said.
BP disputed these figures.
"We've said all along that there's no way to estimate the flow coming out of the pipe accurately," said Bill Salvin, a BP spokesman.
Instead, BP prefers to rely on measurements of oil on the sea surface made by the Coast Guard and the National Oceanic and Atmospheric Administration. Those are also contentious. Salvin also says these analyses should not assume that the oil is spewing from the 21-inch pipe, called a riser, shown in the video.
"The drill pipe, from which the oil is rising, is actually a 9-inch pipe that rests within the riser," Slavin said.
But Wereley says that fact doesn't skew his calculation. And though scientists say they hope BP will eventually release more video and information so they can refine their estimates, what they have now is good enough.
"It's possible to get a pretty decent number by looking at the video," Wereley said.
This new, much larger number suggests that capturing -- and cleaning up -- this oil may be a much bigger challenge than anyone has let on.
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And I'm Renee Montagne, with Lynn Neary.
We'll hear now about a stunning reassessment of the amount of oil spilling into the Gulf of Mexico. According to an exclusive NPR analysis, there's at least 10 times as much oil pouring into the waters as officials estimate.
At NPR's request, experts analyzed video that BP released Wednesday. Their findings suggest that the BP spill is already far larger than the Exxon Valdez spill in Alaska in 1989.
NPR science correspondent Richard Harris has the story.
RICHARD HARRIS: BP has repeatedly said there's no reliable way to measure their oil spill in the Gulf of Mexico by looking at the oil gushing out of the pipe. But scientists say there are actually many proven techniques for doing just that.
We asked professor Steven Wereley at Purdue University to analyze videotape of the sea-floor gusher. He literally co-wrote the book on a technique called PIV.
Professor STEVEN WERELEY (Purdue University): PIV is short for particle image velocimetry and conceptually, it's a very simple technique.
HARRIS: A computer program simply tracks particles, and calculates how fast they're moving. Wereley put the BP video of the gusher into his computer. He made a few simple calculations, and came up with an astonishing value for the rate of the oil spill - much higher than the official estimate of 5,000 barrels a day.
Prof. WERELEY: Seventy thousand barrels a day.
HARRIS: Plus or minus how much?
Prof. WERELEY: Oh, about 20 percent.
HARRIS: How confident are you in that?
Prof. WERELEY: Well, I guess I'm quite confident that it's within the bounds that we just discussed.
HARRIS: Given that uncertainty, the amount of material spewing out of the pipe could be anywhere from 56,000 barrels to 84,000 barrels a day. It is important to note that it's not 100 percent oil. The very short video BP released starts out with a shot of methane.
Prof. WERELEY: And at the end, it seems to be mostly oil. And so there's potentially some fluctuation back and forth between methane and oil.
HARRIS: But assuming that the lion's share of the material coming out the pipe is oil, Wereley's calculations show that the official estimates are way low.
Prof. WERELEY: We're talking more than a factor of 10 difference between what I calculate and the number that's being thrown around.
HARRIS: At least two other calculations back him up.
Timothy Crone, from the Lamont-Doherty Earth Observatory, uses another well-accepted method - different from Wereley's - for calculating fluid flows. He says the flow is at least 50,000 barrels a day.
And Eugene Chiang at the University of California, Berkeley, got a similar answer just using pencil and paper.
Professor EUGENE CHIANG (Astrophysics, University of California, Berkeley): I actually teach a class where the whole point of the class is to estimate things based on very limited amounts of information.
HARRIS: Without even having a sense of the scale from the BP video, he correctly deduced that the diameter of the pipe was about 20 inches. And though his calculation is less precise than Wereley's, it is in the same ballpark.
Prof. CHIANG: I would peg it at around 20,000 to 100,000 barrels per day.
HARRIS: So that's five to 20 times larger than the number we've been using.
Prof. CHIANG: Yeah. If you're using numbers like 5,000 barrels per a day, I would say that's almost certainly incorrect.
HARRIS: And given this flow rate, it seems that this is a spill of unprecedented proportions in United States waters.
Prof. CHIANG: It would just take a few days, at most a week, for it to exceed the Exxon Valdez's record.
HARRIS: BP disputes these figures. Bill Salvin is a company spokesman.
Mr. BILL SALVIN (Spokesman, BP): We've said all along that there's no way to estimate the flow coming out of the pipe accurately.
HARRIS: Instead, BP prefers to rely on measurements of oil on the sea surface made by the Coast Guard and the National Oceanic and Atmospheric Administration. Those are also contentious. Salvin also says these analyses should not assume that the oil is spewing from the 21-inch pipe, called a riser, shown in the video.
Mr. SALVIN: The drill pipe from which the oil is leaking is actually a nine-inch pipe that rests within the riser.
HARRIS: But professor Wereley says that fact does not skew his calculation. And although scientists hope that BP will eventually release a lot more video and information so they can refine their estimates, what they have now is good enough.
Prof. WERELEY: It's possible to get a pretty decent number by looking at the video.
HARRIS: This new, much larger number suggests that capturing and cleaning up this oil may be a much bigger challenge than anyone has let on.
Richard Harris, NPR News. Transcript provided by NPR, Copyright National Public Radio.
