The perplexing physics of oil dispersants
PNAS: News Feature:
May 28, 2019
Massive amounts of oil, gas, and dispersant streamed into the Gulf of Mexico during the Deepwater Horizon disaster. Understanding the chemistry and physics of this mix as it churned through the salt water turns out to be an exceedingly complex problem with plenty of unknowns.
On April 30, 2010, 10 days after a blowout destroyed the offshore drilling platform Deepwater Horizon off the coast of Louisiana and triggered what was fast becoming the worst oil spill in US history, the well’s owner, British Petroleum, sent a remotely piloted submarine 1,500 meters down to the floor of the Gulf of Mexico. Once the vehicle arrived at the broken wellhead, which was still spewing more than 6,000 liters of oil per minute, it stuck the end of a kilometers-long hose into the erupting plume and started pumping in dispersants: detergent-like chemicals designed to fragment the hydrocarbons into tiny droplets. It was the start of a campaign that would ultimately inject the plume with almost 3 million liters of the chemicals.
Using dispersant at that depth was a roll of the dice; the chemicals had been used before on surface oil slicks with varying degrees of success but never in such cold, deep waters. No one could be sure what effect they would ultimately have on the ocean ecosystem, on coastal fisheries, or even on the oil itself. The responders could only hope that the injection would work as intended and that the resulting oil droplets would be consumed by the Gulf’s many petroleum-eating bacteria without ever making it to the surface.