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Proc Natl Acad Sci U S A. 2017 Sep 19;114(38):10065-10070. doi: 10.1073/pnas.1612518114. Epub 2017 Aug 28.

Petroleum dynamics in the sea and influence of subsea dispersant injection during Deepwater Horizon.

Author information

1
School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
2
Zachry Department of Civil Engineering, Texas A&M University, College Station, TX 77843.
3
Zachry Department of Civil Engineering, Texas A&M University, College Station, TX 77843; arey@alum.mit.edu ssocolofsky@civil.tamu.edu.
4
Department of Marine Sciences, University of Georgia, Athens, GA 30602.
5
Center for Natural Resources Development and Protection, Department of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark, NJ 07102.
6
Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543.
7
School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland; arey@alum.mit.edu ssocolofsky@civil.tamu.edu.
8
Department of Environmental Chemistry, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland.

Abstract

During the Deepwater Horizon disaster, a substantial fraction of the 600,000-900,000 tons of released petroleum liquid and natural gas became entrapped below the sea surface, but the quantity entrapped and the sequestration mechanisms have remained unclear. We modeled the buoyant jet of petroleum liquid droplets, gas bubbles, and entrained seawater, using 279 simulated chemical components, for a representative day (June 8, 2010) of the period after the sunken platform's riser pipe was pared at the wellhead (June 4-July 15). The model predicts that 27% of the released mass of petroleum fluids dissolved into the sea during ascent from the pared wellhead (1,505 m depth) to the sea surface, thereby matching observed volatile organic compound (VOC) emissions to the atmosphere. Based on combined results from model simulation and water column measurements, 24% of released petroleum fluid mass became channeled into a stable deep-water intrusion at 900- to 1,300-m depth, as aqueously dissolved compounds (∼23%) and suspended petroleum liquid microdroplets (∼0.8%). Dispersant injection at the wellhead decreased the median initial diameters of simulated petroleum liquid droplets and gas bubbles by 3.2-fold and 3.4-fold, respectively, which increased dissolution of ascending petroleum fluids by 25%. Faster dissolution increased the simulated flows of water-soluble compounds into biologically sparse deep water by 55%, while decreasing the flows of several harmful compounds into biologically rich surface water. Dispersant injection also decreased the simulated emissions of VOCs to the atmosphere by 28%, including a 2,000-fold decrease in emissions of benzene, which lowered health risks for response workers.

KEYWORDS:

Deepwater Horizon; dispersant; offshore drilling; oil spill; petroleum

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