Advances in modeling ultra deep-sea oil spills

Increased world demand in energy has lead to the exploration and exploitation of oil and gas reservoirs in ultra deep waters. The Deepwater Horizon (DWH) was a consequence of such risky endeavors and resulted in an unprecedented oil well blowout in waters 1.5 kilometers deep in the Gulf of Mexico. Yet modeling of deep water petroleum hydrocarbons concentrations remain a challenge. The present work reports the advances and important improvements made in Lagrangian particle tracking: the Connectivity Modeling System oil application developed with the Gulf of Mexico Research Initiative (GOMRI) Consortium for the Integrated Modeling and Analysis of the Gulf Ecosystem (C-IMAGE). Modeling of large-scale oil transport and fate resulting from deep-sea oil spills is highly complex due to a number of bio-chemo-geophysical interactions. Important improvements integrated recent scientific findings from high pressure facilities pertaining to two processes controlling the rising velocity of the oil in the water column: (1) turbulent kinetic energy (TKE) effect on oil droplet size distribution (DSD) and (2) their degassing. The degassing process applies to gas-saturated oil (or live-oil) droplets nucleated with free gas, which then expands inside the droplet due to pressure changes during ascent in the water column. To take into account these processes, we implemented a new multiphase approach with liquid oil and methane gas in the same droplet using log-normal DSD. Our new simulations show a significant increase of the oil reaching the surface despite the initial atomization of oil in micro-droplets. Modeling high-pressure processes on oil and gas released from deep reservoirs helps explain the rapid ascent of oil during the Deepwater Horizon blowout despite small mean droplet size estimates from turbulent kinetic energy dissipation rate models and pressure drop.