Detailed modeling of the dynamic behavior of petroleum in the sea during the Deepwater Horizon accident

Field observations indicate that during the 2010 Deepwater Horizon accident, approximately one quarter of the released petroleum mass became entrapped below the sea surface, but the sequestration mechanisms remain unexplained. A multiphase buoyant plume model is presented that explains field observations in both the sea and atmosphere. The model predicts the independent behavior of hundreds of petroleum compounds and predicts the effect of the changing composition of droplets and bubbles, pressure, and temperature on their properties. It is predicted that emitted gas bubbles experienced a transition to a liquid state due to the preferential dissolution of their lightest components. Subsea dispersant injection, release depth and orifice size, and petroleum composition and flux were the primary factors that led to a predicted 27% of petroleum fluids becoming dissolved into the sea. Without dispersant injection at the pared wellhead (~1500 m depth), we predict that volatile hydrocarbon emissions to the atmosphere would have increased by 40%, increasing exposures of response workers and decreasing exposures of deep-sea biota. The results have implications for environmental impact, human risk, and response strategies during offshore drilling accidents.