ABSTRACT
During a spill, response leadership is frequently tasked with executing urgent decisions with limited supporting data. We have generated a planning tool to assist leadership in identifying response options to subsea oil well blowouts using minimal input data, such as oil and gas flow rate, water depth, and orifice diameter. The presented Response Guidance Table allows for the rapid analysis of blowout dynamics with and without subsea dispersant injection (SSDI) and is intended to provide guidance early on, before detailed models of an accidental release can be created. The Response Guidance Table is based on the analysis of 2,225 simulations of artificial blowout scenarios using Hibernia oil in nearshore and offshore waters of Newfoundland, Canada. The viscous bubble and droplet break-up model in jets (VDROP-J) was coupled with the Texas A&M Oil spill / outfall Calculator (TAMOC) to simulate the fate and transport of oil and gas from the release to the sea surface. Different gas-to-oil ratios and release conditions were modeled, including differing water depth, flow rates, orifice sizes, and ambient current speeds. We analyzed the simulation results to quantify the fraction of oil and gas predicted to surface and the horizontal offset to the surfacing zone. Results varied with water depth and the median size of the initial droplet size distribution. In nearly all simulations, whether SSDI was applied or not, most of the released liquid-phase petroleum was predicted to surface within 14 days. Surfacing fractions of gas and light, aromatic compounds, conversely, depended both on the water depth, release conditions, and application of SSDI. In the deeper simulations, SSDI significantly reduced the fluxes of released gas and volatile compounds, including benzene, to the atmosphere. The results presented in the Guidance Table are applicable to other marine locations around the world with similar water column density profiles and to oil releases of similar composition. This Guidance Table can be used by responders to assess the effectiveness of SSDI during a real spill or to quickly estimate the fate of oil and gas from worst case subsea release scenarios.