REUTERS/hans deryk Hustle and flow the art, science and politics of gauging how much oil is spewing in the gulf

june 2010 hustle and flow june 2010

SCIENTISTS MEASURE THE FLOW SO CONGRESS CAN MEASURE THE BILL special report

• 1,000 barrels a day? 100,000? Depends on who’s counting • Final tally will determine how much BP ends up paying • An oil spill sleuth puzzled by BP’s early estimates

DAMAGE PATROL : U.S. Coast Guard Captain Laferriere points to areas of by deborah zabarenko oil impact, June 21, 2010. REUTERS/SEAN GARDNER

WASHINGTON - Billions of dollars and the future of one the world’s lushest An accurate tally will also help those charged with the clean-up ecosystems could all ride on one elusive number: the precise amount of oil decide which weapons to deploy -- and how many -- to mop up, burn gushing from the broken BP well at the bottom of the . off, corral or collect the mess created by what is easily the worst oil spill in U.S. history. Evidently, it’s not an easy number to calculate. Estimates have ranged from a 1,000 barrels a day to 100,000 barrels a day. Some say it So, given all that is at stake, how can the estimates of what’s coming depends who’s doing the figuring; others point to the unpredictable from that wellhead be so wildly divergent? conditions that go along with drilling for oil deep beneath the seabed. “That’s easy to explain,” said Steven Wereley, who literally wrote the Whatever the final number is, it will help determine how much BP and book on how to make this kind of calculation. “Some of them are wrong.” other operators might have to pay as a result of the April 20 blowout and spill at the rig. One lawsuit has put potential EARLY ESTIMATES: 1,000 VERSUS 95,000 BPD damages -- presuming the oil keeps spewing out until August, as BP has predicted -- at $19 billion. Wereley, a professor of mechanical engineering at Purdue University in Indiana, is a kind of oil spill sleuth. He was one of the first independent experts to put a figure to what was really coming out of the Macondo wellhead, nearly a mile down on the sea floor.

His initial estimate, based on what he saw in a low-resolution 30-second video of the wellhead provided by BP on May 13, was 95,000 barrels per day, or bpd. That counted everything that was spewing from the well, not just oil.

Wereley made that first calculation in response to a reporter’s query about whether it could be done just by looking at the wellhead. Even he reckoned that the figure was high, however, because he didn’t know how much of what he saw bubbling out of the pipe was oil and how much was gas.

He and other scientists who made similar calculations took some heat COOL MECHANICS: BP’s live video feed shows a remotely operated undersea vehicle working from BP over their numbers. on the leaking riser pipe at the site of the spill, June 3, 2010. REUTERS/HO NEW

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”HE MADE IT SOUND LIKE A KINDERGARTEN CLASS COULD DO THIS USING JUST THEIR EYES AND A RULER.”

“The rate of flow from the riser is determined in a number of ways and by a number of variables,” BP said in a May 21 statement. The British oil giant noted that while the riser pipe’s original interior diameter was 19.5 inches, the accident distorted it by about 30 percent, and a drill pipe trapped inside the riser reduced the flow area by another 10 percent.

“Thus, some third party estimates of flow, which assume a 19.5 inch diameter, are inaccurate. As well, there is natural gas in the riser,” the company said. “Data on the hydrocarbons recovered to date suggests that the proportion of gas in the plume exiting the riser is, on average, approximately 50 percent.”

BP spokesman Robert Wine noted the difficulty of early estimates: “Initially there was no way of assessing accurately since there are no meters to measure a leak, and the blowout preventer gauges weren’t able to give any usable information.” Wine said even the government’s first figure of 5,000 bpd, made by calculating the surface area covered by the spreading slick, had a wide margin of uncertainty.

“Subsequent updates have been able to use more data from the blowout preventer and are using the collected flow rates,” Wine said. “But they are still estimates.”

When Wereley and others made their original estimates, however, BP had not yet released information about the oil-to-gas ratio or the dimensions of the misshapen pipe.

Once that data was public, Wereley and other engineers went to work. The oil-to-gas ratio turned out to be 29 percent oil to 71 percent gas; taking that into account, Wereley’s early estimate for the broken well’s oil flow rate was roughly 30,000 barrels a day.

Most of the flow was gas, largely methane, a potent climate-warming chemical that can create oxygen-free “dead zones” in a body of water like the Gulf of Mexico. But methane’s effects are not instantly visible like oil’s.

Among other reasons, the oil flow rate is important because of how the Clean Water Act allows damages to be calculated. If a company is found to have shown gross negligence or willful misconduct in polluting U.S. waters, it can be ordered to pay $4,300 for every barrel of oil spilled. To understand this method, think of some clouds floating across the Coast Guard Admiral Thad Allen was blunt in mid-June: “That’s the sky. They don’t change their shape constantly, so if you see something $100,000 question -- we need a flow rate. And we’re never going to that looks like a lamb, you can track it for a while as it moves with the know exactly what it is until we have a tight seal on that and we can wind. actually measure production.” Now take a look at online video of the BP wellhead -- some early, GLOBS, CHUNKS AND BILLOWS low-resolution video is available at http://www.youtube.com/ watch?v=Y5hFPI4Y93U -- and you can see some cloud-like billows It turns out that there is a way to calculate what’s coming out of the coming out of the broken pipe. well without putting a meter on the leak, and that is particle image velocimetry. Wereley and three colleagues wrote a book on this subject, Experts in fluid mechanics, people who study how liquids act, call “Particle Image Velocimetry: A Practical Guide,” published in 2007. these cloud-like formations turbulent structures.

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Wereley said it took him two hours to look at the ones he saw on the The outer diameter of the riser pipe is 21.5 inches. Wereley figured May 13 BP video and calculate how much was coming from the well. out how many pixels that was in the video, and from that was able to He made it sound like a kindergarten class could do this using just calculate the size of the turbulent structures and how fast they were their eyes and a ruler. moving in inches per second. He then used that figure to calculate how much was coming out, and how fast, producing a figure measured in “It’s not rocket science,” Wereley said. “It’s not that hard once you barrels per day. know what you’re doing.” That figure, which Wereley arrived at using computer codes that make After all, he said, what you’re doing is calculating a rate -- the number thousands of measurements, was 70,000. of barrels of oil leaking each day -- and rate equals distance over time. But fluid mechanics can be a tricky business, especially with an Here’s how he explained it: “If you watch the videos in slow-motion ... you’ll opaque liquid like oil. see globs of fluid ... some identifiable chunk or billow ... and you’ll see they’re carried downstream by the flow, away from the exit of the pipe. “but fluid mechanics can be a “Measuring the speed of these things is pretty easy. Basically if you see one of these structures at some location in one image, and you tricky business.” see that it’s moved in the next image ... then all I need to know is what is the time between these two images. And that’s encoded in the movie, which plays back at a certain speed so many frames per While Wereley and other experts could reasonably estimate the speed second.” and amount of oil coming from the outside of the jet of oil spurting from the pipe, they didn’t know for certain how fast the oil coming You put your ruler on the spot where the glob was in the first frame from the inside of the jet was going -- because they couldn’t see it. It and then on the spot it moved to in the second frame, measure the was obscured by the dark oil at the outside. difference between them and voila! You have the speed at which this glob of oil and gas moved. Except that it’s in pixels per second, not in Imagine it this way: you can see all of the water coming from a faucet, any real-world dimension. no matter what the diameter of the faucet is, because water is clear. But what if chocolate syrup suddenly started pouring out of the SITUATION FLUID faucet? You’d be able to see the syrup on the outside of the stream coming from the tap, but you’d only be able to guess at what was on For a real-world measurement, you’d need to be able to compare the the inside, because chocolate syrup is opaque, like oil. globs and their movement to a stationary object that’s also in the video, whose size you know for sure. That would be the broken riser pipe from If you knew a bit about fluid mechanics, you’d probably assume that which all the globs are spilling. That pipe is, for now, not going anywhere. the center of the flow -- the part you can’t see -- is moving a bit faster than the chocolate syrup at the edges.

THE MIDDLE MOVES FASTER

Why? Because the stuff in the middle is largely unaffected by things at the edges that work to slow liquid down. In the chocolate syrup example, the inside of the faucet and possibly the air in the room could act as a drag on the outside of the chocolate stream.

Similar forces apply to the oil coming out of the broken wellhead. The sea water around it acts as a brake on the oil on the outside of the stream, without having as much of an effect on the oil that’s on the inside, Wereley said.

Mindful of BP’s criticism of his initial estimate, Wereley wanted to be conservative when he was working on his updated calculation. So he based it on the assumption that the flow inside the jet of oil was moving at about the same speed as the flow at the outside of the jet, all UNDER OATH: Interior Secretary Ken Salazar watches BP footage of the gushing pipe as he testifies at the Senate but guaranteeing that the estimate would be on the Environment and Public Works Committee hearing, May 18, 2010. REUTERS/KEVIN LAMARQUE low side.

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Until mid-May, Wereley and other experts -- including Timothy A HYPOTHETICAL WORST CASE Crone of Columbia University’s Lamont-Doherty Earth Observatory and Eugene Chiang at the University of California-Berkeley -- were Soon after Wereley’s testimony, he was chosen as a member of the working on their own on this question. government’s Flow Rate Technical Group, a collection of academics whose job it is to determine the magic flow rate number. Then Congress got involved, and things changed. “The government doesn’t want to trust a couple of scientists working On May 19, Representative Ed Markey, the Massachusetts Democrat in their spare time, so they set up the Flow Rate Technical Group to who chairs the House global warming subcommittee, asked BP to come up with an official government-sanctioned number,” he said. show the public live high-resolution video from the broken wellhead. (This video feed is available at http://globalwarming.house.gov/ The team studied the new high-resolution spill-cam video, and spillcam) estimated the flow at 20,000 to 40,000 barrels a day, before the June 3 operation to cut the riser and cap it so oil could be collected Wereley testified that day, along with Frank Muller-Karger, a and sent up to the surface. After that June 3 procedure, the flow was University of South Florida professor of biological oceanography. estimated at 35,000 to 60,000 bpd. Wereley couldn’t fathom any realistic way BP’s estimate of the flow rate at that time -- 5,000 barrels per day -- could be right. After that, Wereley considered the technical group’s job largely complete, but that was before an underwater robot bumped into a Lamar McKay, BP America’s president, said at the hearing that containment cap on the wellhead on June 23, prompting BP to take it officials still couldn’t say which estimates were correct. The higher off to assess any damage. The result: a new surge of oil until the cap estimates were “theoretically possible,” he said, “but I don’t think was reinstalled 10 hours later. anyone who’s been working on this thinks it’s that high.”

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“if you’re throwing around numbers like 100,000 barrels per day, you know pretty well that it’s not 1,000 barrels per day.”

UNDER PRESSURE: BP Chairman Carl-Henric Svanberg speaks to the media after meeting with U.S. President Obama at the in Washington. BP CEO takes a back seat alongside Managing Director and the Chairman in the Americas, Lamar McKay, June 16, 2010. REUTERS/JIM YOUNG

Even an untrained eye could see the difference between the flow Wereley did not hazard a guess about how likely this is, calling it with the cap on and the increased flow with the cap removed. Which hypothetical. brings up BP’s worst-case-scenario estimate of 100,000 barrels per day, provided to Congress in early May and publicized the following “But what it also tells you is, if you’re throwing around numbers like month by Markey. 100,000 barrels per day, you know pretty well that it’s not 1,000 barrels per day. It stands to reason that if you put the blowout While 100,000 barrels per day is a high number, the company preventer on there, it’s not going to stop 99 percent of the flow. They document that mentions it calls this a low probability scenario of should have expected a much larger flow than 1,000 barrels per day.” what could happen if the blowout preventer -- which didn’t prevent a blowout but which is still keeping some percentage of the oil and gas (Additional reporting by Kristen Hays in Houston and Steve Holland in from leaking -- and the wellhead were removed. Washington; Editing by Jim Impoco and Claudia Parsons)

COVER PHOTO: Workers use a containment boom to capture oil close to the site of the BP oil spill in the Gulf of Mexico as Discover Enterprise drill ship is seen in the background approximately 40 miles off the coast of Louisiana, May 18, 2010. REUTERS/hans deryk

For more information contact: Jim Impoco, Enterprise Editor, Americas Claudia Parsons, Deputy Enterprise Editor Deborah Zabarenko, Environment Correspondent +1 646 223 8923 +1 646 223 6282 +1 202 898 8388 [email protected] [email protected] [email protected]

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