Friday, January 13, 2012

Chemical Measurements Confirm Official Estimate of Gulf Oil Spill Rate

By combining detailed chemical measurements in the deep ocean, in the oil slick, and in the air, NOAA scientists and academic colleagues have independently estimated how fast gases and oil were leaking during the 2010 Deepwater Horizon oil spill in the Gulf of Mexico.

The new chemistry-based spill rate estimate, an average of 11,130 tons of gas and oil compounds per day, is close to the official average leak rate estimate of about 11,350 tons of gas and oil per day (equal to about 59,200 barrels of liquid oil per day).

"This study uses the available chemical data to give a better understanding of what went where, and why," said Thomas Ryerson, Ph.D., a NOAA research chemist and lead author of the study. "The surface and subsurface measurements and analysis provided by our university colleagues were key to this unprecedented approach to understanding an oil spill."

The NOAA-led team did not rely on any of the data used in the original estimates, such as video flow analysis, pipe diameter and fluid flow calculations. "We analyzed a completely separate set of chemical measurements, which independently led us to a very similar leak estimate," Ryerson said.

The new study, Chemical data quantify Deepwater Horizon hydrocarbon flow rate and environmental distribution, was published online January 9 in the journal Proceedings of the National Academy of Sciences.

The new analysis follows on another NOAA-led study published last year, in which Ryerson and colleagues estimated a lower limit to the Deepwater Horizon leak rate based on two days of airborne data collected during the spill and the chemical makeup of the reservoir gas and oil determined before the spill. The new analysis adds in many other sources of data, including subsurface and surface samples taken during six weeks of the spill and including a direct measure of the makeup of the gas and oil actually leaking into the Gulf.

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