The Use of Dispersants in Marine Oil Spill Response (2020) / Chapter Skim
Currently Skimming:
APPENDIX E: CONSULTANTS' REPORT
APPENDIX E: CONSULTANTS' REPORT
Pages 297-324
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 297... ...
(2017) published a dataset derived from the Deepwater Horizon measurements, which, after close review, the committee felt represented a reasonable benchmark for testing droplet models.
|
From page 298... ...
. Model output includes dissolved concentrations in the deepwater intrusion layer, mass flow rate of compounds to the air/water interface, and water column concentrations between the intrusion layer and sea surface.
|
From page 299... ...
Section 7 explains our method to compute dissolved concentrations between the intrusion layer and the sea surface, where individual Lagrangian bubbles and droplets transit the water column. This section also shows sample results for benzene.
|
From page 300... ...
We show the model predictions compared to measured field data in Figure E.5, using the same figure format as in Figure E.2. In this case, the simulation under-predicts the fraction of released petroleum entering the intrusion layer.
|
From page 301... ...
FIGURE E.2 Simulation results for Case 1.
|
From page 302... ...
302 THE USE OF DISPERSANTS IN MARINE OIL SPILL RESPONSE FIGURE E.3 Simulated fate and transport of petroleum fluids for Case 1 without calibrated microdroplets. FIGURE E.4 Initial bubble and droplet size distribution for Case 2.
|
From page 303... ...
FIGURE E.5 Simulation results for Case 2.
|
From page 304... ...
304 THE USE OF DISPERSANTS IN MARINE OIL SPILL RESPONSE FIGURE E.6 Simulated fate and transport of petroleum fluids for Case 2 without calibrated microdroplets. FIGURE E.7 Initial bubble and droplet size distribution for Case 4.
|
From page 305... ...
FIGURE E.8 Simulation results for Case 4.
|
From page 306... ...
We show the model predictions compared to measured field data in Figure E.8, using the same figure format as in Figure E.2. In the intrusion layer (Panels A and B)
|
From page 307... ...
We show the model predictions compared to measured field data in Figure E.11, using the same figure format as in Figure E.2. In this case, the simulation significantly over-predicts the fraction of released petroleum entering the intrusion layer, especially for the insoluble compounds.
|
From page 308... ...
308 FIGURE E.11 Simulation results for Case 5.
|
From page 309... ...
Because dispersants were injected on June 8, 2010, this untreated case represents a hypothetical sensitivity study with respect to the true hindcast, which would include the effect of dispersant injection. We show the model predictions compared to measured field data in Figure E.14, using the same figure format as in Figure E.2.
|
From page 310... ...
, but the lighter compounds remain over-predicted in the intrusion layer, suggesting more dissolution is occurring in the model than was observed. This is consistent with an under-predicted droplet size, and is corroborated by the predictions at the sea surface, which show much less oil reaching the surface in the model than the observations.
|
From page 311... ...
FIGURE E.14 Simulation results for Case 6.
|
From page 312... ...
312 THE USE OF DISPERSANTS IN MARINE OIL SPILL RESPONSE FIGURE E.15 Simulated fate and transport of petroleum fluids for Case 6 without calibrated microdroplets. FIGURE E.16 Initial bubble and droplet size distribution for Case 7.
|
From page 313... ...
FIGURE E.17 Simulation results for Case 7.
|
From page 314... ...
For injury assessment, the concentrations of dissolved hydrocarbons throughout the ocean water column are needed. These are not immediately available because oil droplets and gas bubbles rise as individual Lagrangian particles between the deep intrusion layer and the surface, and there is no associated control volume of seawater to use to track the dissolved concentrations.
|
From page 315... ...
We compute these concentrations for each chemical component in the gas bubbles and oil droplets above the intrusion layer using our full 279 pseudo-component model of the Deepwater Horizon reservoir fluid. We compute all concentrations at a distance 10 km downstream of the broken Macondo wellhead, and the total concentration of a given chemical component is the superposition of the contributions from each bubble and droplet size in each simulation.
|
From page 316... ...
The currents change direction with height, and at each depth, we assume that all bubbles are aligned on a single x-axis, parallel with the currents. Figure E.20 plots the currents we used for all our simulations, which were measured near the Deepwater Horizon wellhead by a near-surface, down-looking acoustic Doppler current profiler (ADCP)
|
From page 317... ...
FIGURE E.20 Measured ocean currents near the Deepwater Horizon wellhead on June 8, 2010.
|
From page 318... ...
FIGURE E.21 Profiles of the concentration of benzene for Case 4 at a location 10 km downstream of the Deepwater Horizon at three different depths, and along lines normal to the crossflow. Note that different y-axis scales are used to make the plots readable.
|
From page 319... ...
In Figure E.21, we present the profiles benzene for Case 4 at three different depths at a distance of x = 10 km downstream of the Deepwater Horizon wellhead, hence, profiles extracted from Figure E.19. Peak concentrations occur low in the water column, close to the intrusion layer, and are on the order of 10–7 kg/m3 (10–9 mol/l)
|
From page 320... ...
320 FIGURE E.22 Comparison of the simulation results for Cases 2, 4, and 7.
|
From page 321... ...
500 600 700 800 900 -10 -9 -8 -7 -6 -5 -4 -3 10 10 10 10 10 10 10 10 C (kg/m 3 ) FIGURE E.23 Vertical profiles of the maximum dissolved benzene concentration for Cases 2, 4, and 7 at a location 10 km downstream of the Deepwater Horizon wellhead.
|
From page 322... ...
Because the three Cases 2, 4, and 7 are all based on the same model assumptions and because Case 4 gives the best match between the model predictions and the observations, these cases may be considered as reliable predictors for the effect of subsea dispersant injection on the Macondo oil during the Deepwater Horizon accident. The DORs used during the accident were lower than optimal, but resulted in some liquid oil not reaching the sea surface and significantly improved air quality by suppressing atmospheric emissions of VOCs by 28%, including a 2,000 times reduction of benzene emission.
|
From page 323... ...
2012. Chemical data quantify Deepwater Horizon hydrocarbon flow rate and environmental distribution.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.