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Wed Dec 5, 2012, 11:53 AM

Numerical study suggests subsea injection of chemicals didn't prevent oil from rising to sea surface

http://www.eurekalert.org/pub_releases/2012-12/uomr-nss120412.php
Public release date: 4-Dec-2012

Contact: Barbra Gonzalez, UM Rosenstiel School
barbgo@rsmas.miami.edu
305-421-4704
University of Miami Rosenstiel School of Marine & Atmospheric Science

Numerical study suggests subsea injection of chemicals didn't prevent oil from rising to sea surface

Groundbreaking 3D models show that oil droplets were too small for dispersants to have significant impact

MIAMI December 4, 2012 - The 2010 blowout of the Macondo well in the waters of the Gulf of Mexico resulted in the region's largest oil spill in U.S. history. As the Deepwater Horizon (DWH) incident unfolded, in an effort to prevent the oil from coming to the surface and reaching coastal and marsh ecosystems, chemical dispersants were injected at the wellhead. These powerful dispersants, typically used to break up oil slicks at the sea surface had never been used in such large quantities and over such a prolonged period of time in the deep ocean.

A new study published in Environmental Science & Technology, led by University of Miami (UM) Rosenstiel School of Marine & Atmospheric Science Associate Professor of Applied Marine Physics Claire Paris, is the first to examine the effects of the use of unprecedented quantities of synthetic dispersants on the distribution of an oil mass in the water column, based on a modeling approach. The team of researchers included UM Rosenstiel School Assistant Scientist Matthieu Le Henaff and Research Associate Professor Villy Kourafalou, UM Center for Computational Science (CCS) Scientist Judith Helgers and Research Associate Professor Ashwanth Srinivasan, Ph.D. Candidate Zachary Aman from Colorado School of Mines, Research Associate Professor Ajit Subramaniam from Lamont Doherty Earth Observatory at Columbia University, and Professor Dong-Ping Wang from the School of Marine and Atmospheric Science of SUNY at Stony Brook. Together they developed and tested models to show that the application of oil-dispersing chemicals had little effect on the oil surfacing in the Gulf of Mexico.

"Deepwater drilling into large, high-pressure reservoirs of oil and gas located far offshore and hundreds of meters below the ocean's surface involves risks for which we were not adequately prepared," said Paris. "As the oil gushed uncontrolled into the Gulf, injection of chemical dispersant into the deep ocean may have had little effect because the oil was coming out with such pressure that it was already dispersed in small droplets. It is impossible to know whether the synthetic dispersant was well mixed with the oil as it was injected. Our models treat both scenarios, and regardless of whether you have the dispersant in the water mixture or not, the amount of oil reaching the sea surface remained relatively unchanged."

The researchers estimated the distribution of oil droplet sizes with and without injection of dispersant at the wellhead. They then applied a novel oil-mass tracking model of the Connectivity Modeling System (CMS) developed shortly after the DWH incident with a RAPID award from the National Science Foundation (NSF) and presented a three-dimensional simulation of the DWH spill showing the unfolding of the disaster to examine the effect the synthetic dispersant may have had on the oil transport in the water column. The model indicated that the dispersant injected at BP's Macondo wellhead was not necessary to break up the oil. The subsea application of dispersant did not have its expected outcome.

http://dx.doi.org/10.1021/es303197h

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