Trajectory modeling in support of the Shell Shelburne Basin Exploration Drilling Program

Accidental discharges of hydrocarbons were modeled by RPS at representative sites throughout the Shell Exploration Licenses. This included the trajectory and fate modeling of hypothetical releases of crude oil from deep-water blowouts at multiple depths, and surface releases of diesel. OILMAP Deep was used to characterize the near-field conditions of the blowout in the region directly around the wellhead. These results were used to initialize the SIMAP modeling system, which assessed the transport and fate of hydrocarbons throughout the environment. Stochastic analyses provided probabilistic results specifying the likelihood and extent of multiple specific threshold exceedances of surface oil thickness, shoreline oil mass, and in water contamination. Deterministic analyses provided specific trajectory and mass balance information for representative 95th percentile cases of surface, shore, and water column contamination. The goal was to determine the range of effects that may be expected in the event of a release and were included in the EIA.

RPS also modeled accidental and operational drilling discharges that may be possible with the exploratory drilling. Using RPS’s MUDMAP model, the effects from operational discharges of mud and cuttings, as well as accidental releases of synthetic based mud (SBM) originating at the sea surface and the marine riser were determined for the same representative sites. This modeling assessed seabed depositions and total suspended solid concentrations associated in the water column and were included in the EIA.

The effects of surface and subsurface dispersant applications were modeled by RPS at the same representative sites and identified deterministic scenarios. RPS’s OILMAP Deep modeling package was used to conduct a sensitivity analysis identifying the optimal dispersant application volumes for multiple blowout conditions, and characterized the near-field plume dynamics. RPS’s SIMAP model was then used to determine the fate and trajectory of hydrocarbons for dispersant mediated cases. Results between the dispersant mediated and unmitigated cases were then compared to provide an assessment of likely differences in effects. These findings were used to inform the NEBA.

Finally, a Risk Assessment was conducted (with Environmental Research Consulting, Inc.) to evaluate the spillage probabilities and volumes for identified scenarios. Additionally, oil inputs in the region were investigated in a benchmarking analysis. The modeled blowout scenarios were then compared to other significant blowouts with respect to the release rate, duration, and total volume. These results were summarized in the RA.

RPS uses its model systems to provide a range of services to industry and government clients, including oil spill risk assessments (OSRP, EIA, NEBA, RA) and expert testimony.