Critics question plans to spray dispersant in future deep spills
PHOTO: ENERGY AND MINERALS INSTITUTE AT THE UNIVERSITY OF WESTERN AUSTRALIA
I
busted wellhead? If they were relatively large—more than 100 to 300 microns, depending on who you ask—they would have been buoyant, and the dispersant could have helped stop their swift rise by breaking them up. Smaller droplets, however, can become suspended in the water like fog and may never surface, meaning dispersant may not make much difference. Paris and her research partner, chemical engineer Zachary Aman, used one of the world’s toughest blenders to try to solve the puzzle. The mixer, housed at Aman’s lab at the University of Western Australia, Crawley, is the size of a champagne glass, made of industrial sapphire strong enough to contain pressures 120 times greater than that found at Earth’s surface—roughly the same as 1200 meters beneath the ocean surface. After oil impregnated with natural gas is mixed with salt water, stainless steel blades spin at up to 2000 revolutions per
SCIENCE sciencemag.org
3 APRIL 2015 • VOL 348 ISSUE 6230
Published by AAAS
Downloaded from www.sciencemag.org on April 5, 2015
minute, generating turbulence that shreds the oil into drops. A high-speed camera n the early weeks of the 2010 captures the action. Deepwater Horizon oil spill, as the In blender experiments, the researchers ruptured wellhead spewed plumes of found that the pressure and turbulence oil, desperate engineers took a gamble at the Deepwater wellhead would have on a tactic they had never tried before. created droplets so small—80 microns in They rigged a hose to inject a toxic disperdiameter on average—that many wouldn’t sant, normally used to break up surface reach the surface. That suggests “you may oil slicks, into the hot, gas-rich petroleum not get a huge benefit from the disperjetting from the sea floor 1500 meters sant,” Aman says. below the Gulf of Mexico’s surface. They Skeptics argue that Aman is comhoped the dispersant, which chemically mitting a crucial error by likening the acts like a soap, would break up much of forces created by a spinning blender to the oil into a fine undersea mist, preventthe turbulence created at a gushing pipe, ing it from bubbling up to the surface and which acts more like the nozzle of a fire smothering shorelines. hose. Aman’s findings also run counter Today, many observers consider the to other studies that find bigger droplets, move a remarkable success and say that critics note. “We think they definitely it helped blunt the spill’s impacts on made a mistake, and this is a hot-button coastal ecosystems (see main story, policy question,” says Scott Socolofsky, p. 22). As a result, U.S. and international an engineer at Texas A&M University, agencies are starting to write the use of College Station. deep-sea dispersant into plans for hanLabs around the world are now trying dling future spills. The to find a more definitive oil industry is designing answer. In the United special dispersant hardStates, Canada, and ware for wellheads. Germany, groups But a few scientists are preparing to run tests question whether that better approximate pumping 2.9 million deep-sea drilling condiliters of the chemicals tions. Aman himself is into the deep sea really fine-tuning computer did much good (and models that he believes whether it may actually will create a more realishave harmed sea life). If tic picture of the forces at a similar spill occurred play near the wellhead. today, “I would definitely But given the difsay not to use the [deepficulty of mimicking sea] dispersant,” says the conditions at an Claire Paris, an oceanogundersea blowout, it’s rapher at the University not clear that “if we of Miami in Florida and have this conversation one of the researchin 2 years that we’re ers raising concerns. going to be any better In February, she cooff,” says Steve Lehmann, authored a paper online a senior science adviser in Chemical Engineering at the National Oceanic Science that concluded and Atmospheric the dispersant reduced Administration in the amount of floating Lowell, Massachusetts, oil by just 1% to 3%. who deals with spill The debate centers response. And that, he on a seemingly simple says, “is a concern” for question: How big were officials who will have to Researchers use this high-pressure chamber to study how oil behaves under the droplets of oil that decide whether deep-sea conditions like those at the Deepwater wellhead. billowed, like ash clouds dispersant should be from a volcano, from the de rigueur. ■ By Warren Cornwall
27
PHOTO: ENERGY AND MINERALS INSTITUTE AT THE UNIVERSITY OF WESTERN AUSTRALIA
I
busted wellhead? If they were relatively large—more than 100 to 300 microns, depending on who you ask—they would have been buoyant, and the dispersant could have helped stop their swift rise by breaking them up. Smaller droplets, however, can become suspended in the water like fog and may never surface, meaning dispersant may not make much difference. Paris and her research partner, chemical engineer Zachary Aman, used one of the world’s toughest blenders to try to solve the puzzle. The mixer, housed at Aman’s lab at the University of Western Australia, Crawley, is the size of a champagne glass, made of industrial sapphire strong enough to contain pressures 120 times greater than that found at Earth’s surface—roughly the same as 1200 meters beneath the ocean surface. After oil impregnated with natural gas is mixed with salt water, stainless steel blades spin at up to 2000 revolutions per
SCIENCE sciencemag.org
3 APRIL 2015 • VOL 348 ISSUE 6230
Published by AAAS
Downloaded from www.sciencemag.org on April 5, 2015
minute, generating turbulence that shreds the oil into drops. A high-speed camera n the early weeks of the 2010 captures the action. Deepwater Horizon oil spill, as the In blender experiments, the researchers ruptured wellhead spewed plumes of found that the pressure and turbulence oil, desperate engineers took a gamble at the Deepwater wellhead would have on a tactic they had never tried before. created droplets so small—80 microns in They rigged a hose to inject a toxic disperdiameter on average—that many wouldn’t sant, normally used to break up surface reach the surface. That suggests “you may oil slicks, into the hot, gas-rich petroleum not get a huge benefit from the disperjetting from the sea floor 1500 meters sant,” Aman says. below the Gulf of Mexico’s surface. They Skeptics argue that Aman is comhoped the dispersant, which chemically mitting a crucial error by likening the acts like a soap, would break up much of forces created by a spinning blender to the oil into a fine undersea mist, preventthe turbulence created at a gushing pipe, ing it from bubbling up to the surface and which acts more like the nozzle of a fire smothering shorelines. hose. Aman’s findings also run counter Today, many observers consider the to other studies that find bigger droplets, move a remarkable success and say that critics note. “We think they definitely it helped blunt the spill’s impacts on made a mistake, and this is a hot-button coastal ecosystems (see main story, policy question,” says Scott Socolofsky, p. 22). As a result, U.S. and international an engineer at Texas A&M University, agencies are starting to write the use of College Station. deep-sea dispersant into plans for hanLabs around the world are now trying dling future spills. The to find a more definitive oil industry is designing answer. In the United special dispersant hardStates, Canada, and ware for wellheads. Germany, groups But a few scientists are preparing to run tests question whether that better approximate pumping 2.9 million deep-sea drilling condiliters of the chemicals tions. Aman himself is into the deep sea really fine-tuning computer did much good (and models that he believes whether it may actually will create a more realishave harmed sea life). If tic picture of the forces at a similar spill occurred play near the wellhead. today, “I would definitely But given the difsay not to use the [deepficulty of mimicking sea] dispersant,” says the conditions at an Claire Paris, an oceanogundersea blowout, it’s rapher at the University not clear that “if we of Miami in Florida and have this conversation one of the researchin 2 years that we’re ers raising concerns. going to be any better In February, she cooff,” says Steve Lehmann, authored a paper online a senior science adviser in Chemical Engineering at the National Oceanic Science that concluded and Atmospheric the dispersant reduced Administration in the amount of floating Lowell, Massachusetts, oil by just 1% to 3%. who deals with spill The debate centers response. And that, he on a seemingly simple says, “is a concern” for question: How big were officials who will have to Researchers use this high-pressure chamber to study how oil behaves under the droplets of oil that decide whether deep-sea conditions like those at the Deepwater wellhead. billowed, like ash clouds dispersant should be from a volcano, from the de rigueur. ■ By Warren Cornwall
27
