Marine Oil Fate: Knowledge Gaps, Basic Research, and Development Needs; A Perspective Based on the Deepwater Horizon Spill

The various complex forms of transport as well as many other fate processes ongoing in the marine water column require research for the understanding and prediction of impacts of deepwater releases on the marine ecosystem. Such research is useful for assessing the context and limits of future deepwater oil and gas development in the Gulf of Mexico. The Deepwater Horizon incident in the Gulf represents the first oil spill occurring at significant depth, similar to 5,000 ft (1,500 m). It is also the first situation where dispersants were directly added to the hydrocarbon effluent from the wellhead in efforts to disperse the droplets over a large volume of the water column. In this regard, this perspective is an original work in that it provides an in-depth analysis of gaps and needs, which will guide future work in the field. Preliminary reports have led to a variety of images that highlight new physiochemical phenomena whose comprehensive understanding will be needed in assessing the oil and associated hydrocarbon chemical fate and environmental impact. Camera images of the oil and gas entering the water at depth and subsurface remote-operated vehicles have revealed droplet clouds and hydrocarbon plumes suspended thousands of feet below the surface moving horizontally with the water currents. Although preliminary, these and other observations are sufficient to piece together new hypothetical deepwater chemodynamic processes and phenomena that have yet to be fully understood. This position article focuses on unique and new research issues raised and relevant to this spill specifically. The ultimate fate of the oil constituents is a very broad subject. Our objective was concerned with the deepwater spill-initiating event. We focused on selected fate processes associated with the oil and dispersant chemodynamics from the blowout point, on the seabed, in the water column upward, and finally, into the marine surface mixed layer. An observation-conceived, process-based, mass balance-crafted engineering science predictive tool is proposed. It is needed for forecasting, projecting in anticipation of and managing the next spill, and answering the question where does it all go?