ITAC – Industry Technical Advisory Committee
for Oil Spill Response
Wednesday, October 24, 2016
Dr. Victoria Broje
Subsea Dispersants – D3
Research Projects on Subsea Dispersants

Effectiveness

Modelling

Fate and Effects

Monitoring

New projects (VOC modelling,
marine snow literature review,
biodegradation modelling)

Comparative Risk Assessment

Communication Efforts
Exxon
Scaled Testing of Subsea Dispersant Effectiveness
Scope:
• Phase I – evaluated injection methods & DOR using a tower basin,
Corexit® 9500 dispersant & one crude oil
• Phase II – tested other oils and dispersants using a tower basin
• Phase III – studied high pressure conditions with dead oil using a
high pressure test tank
• Phase IV – evaluated latent breakup (tip streaming) using an
inverted cone system
• Phase V – tested high pressure
conditions with live oil / associated
gas using a high pressure test tank
• Phase VI – larger scale testing using
the Ohmsett wave basin
Scaled Testing of Subsea Dispersant Effectiveness
Conclusions:
• SSDI significantly reduced oil droplet sizes
• Effectiveness depends on the oil type, dispersant & dosage
• Injection methods were evaluated
• New approach for predicting droplet sizes (modified Weber)
• Results don’t support statements that SSDI during DWH spill was
unnecessary due to small size of naturally dispersed oil droplets
• The scaled testing indicates that SSDI effectiveness is not
dependent on pressure
• Developed new monitoring equipment (droplets & bubbles
detection)
Numerical Modeling of Deepwater Plumes
Scope: Comparison of most used integrated plume trajectory
models
• SINTEF (OSCAR) and DeepBlow model as the integrated
nearfield plume model, Plume-3D
• National Energy Technology Laboratory (NETL) Blowout and Spill
Occurrence Model (BLOSOM)
• The MIKE by DHI Oil Spill (OS) module, with integrated nearfield
plume model and Lagrangian and Eulerian model for the farfield
• RPS ASA’s OILMAP, which includes the OILMAPDeep module as
the integrated near-field plume model
• A hybrid modeling approach of empirical and Lagrangian particle
tracking models
Numerical Modeling of Deepwater Plumes
Modelers ran 14 simple but realistic scenarios with and without
subsea dispersant injection in deep and shallow water for high
and low gas-oil ratio and in weak to strong cross-flows
Conclusions:
• Initial droplet size distribution and the rates of the fate
processes are critical to improving confidence in model
predictions
• Validated with observations made at
Macondo, published SINTEF lab data
and DeepSpill data
• Results were reviewed at a workshop
• Publication – Sokolofsky et al, 2015
Conclusions:
• Oil degrading microorganisms occur
even in extreme marine
environments that are cold, deep,
and under high pressure;
• Microbial communities can rapidly
shift to hydrocarbon degraders;
• Oil diluted to realistic concentrations
is expected to biodegrade in deep
waters; and
• Further biodegradation testing not
deemed a high research priority for
further API funding given current and
on-going work in this topic.
http://hazenlab.utk.edu/files/pdf/
2016Hazen_etal_EST_Feature.pdf
Role of Pressure on Hydrocarbon Toxicity
Scope:
• Develop an understanding of the effects of pressure and
gasses on potential toxicity of dispersed oil at depth
Approach:
• Review literature on the effect of pressure on toxicity of
narcotic chemicals including hydrocarbons
• Use available toxicity models to predict the toxicity of C1 to
C4 gases and assess the relative contribution of dissolved
phase gases in contributing to aquatic toxicity
Conclusion:
• Toxicity testing of baro-tolerant deep sea species at
ambient pressure likely conservative; avoiding safety
concerns / costs for toxicity tests at elevated pressure
Solubility/Toxicity of Oil Components at Depth
Scope:
• Identify and compare models that can predict the solubility
and toxicity of oil and dispersants under deep sea conditions
Approach:
• Used a proven fate model to predict dissolved
concentrations of oil components and used those in an
effect model to predict toxicity
• Dissolved oil and gas component exposures from several
scenarios were simulated using the SINTEF OSCAR model
coupled to the HDR pressure-dependent toxicity model;
Conclusion:
• Results showed dissolved gases have a limited role (≤1.4%)
in contributing to predicted toxicity
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Scope:
• Assess the relative sensitivity of baro-tolererant species
Approach:
• Conduct toxicity tests using constant, single hydrocarbon (toluene,
methyl naphthalene, phenanthrene) and dispersant (Corexit 9500)
exposures with three baro-tolerant species at 1 atm pressure
• Conduct physically and chemically dispersed oil toxicity tests at 1 atm
with two deep sea species
• Compare to shallow-water species SSD
Conclusion:
• Data so far indicate that deep-sea species have similar toxicological
responses to whole oil or individual oil components, and are
comparable to shallow water species.
Lophelia pertusa
Anoplopoma
fimbria
Pandalus borealis
Evaluated existing and emerging
monitoring technologies
◦ White paper developed
◦ Results presented at Clean Gulf
2012
Developed industry recommended
monitoring plan for SSDI
http://www.spillprevention.org/documents/AP
I%201152-Industry-Recommended-SubseaDispersant-Monitoring-Plan.pdf
Developing
“Industry Guidelines on requesting
Regulatory Concurrence for
Subsea Dispersant Use”
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New Projects
• Review of Oil Degradation Models
Investigate the algorithms used to characterize degradation
processes in oil fate models and identify opportunities to foster
consistency and state-of-the-science
• Marine Snow in the Context of Oil Spill Response
Conduct literature review on marine snow in unpolluted marine
environments and in presence of oil; effect of dispersants on
marine snow formation; DWH and other spills data; conceptual
models and study designs.
• Modeling Volatile Organic Compound (VOC)
Concentrations in Air
Model VOC concentrations at the water surface near blowout site
and evaluate effect of SSDI on VOC concentrations.
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Comparative Risk Assessment
Goal
• To compare the relative risks and tradeoffs of different oil spill response
options in a hypothetical deepwater blowout scenario
• Relative response options comparison. Not a NRDA.
Approach
• RPS/Ramboll/Environ team in collaboration with Technical Advisory
Committee (TAC)
• Oil spill trajectory modeling to define volumes of water, area of sea surface,
length of shoreline with oil above pre-defined thresholds
• Estimate fraction of VECs within ecosystem compartments exposed to oil
above threshold
• Evaluate exposure and recovery potential for each VEC
• Compare of the relative risks and tradeoffs to ECs and VECs associated
with deployment of different oil spill response options
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Comparative Risk Assessment
Modeling Parameters
RPS
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Comparative Risk Assessment
• Two trajectories were selected from 100 stochastic model runs
(randomizing start date and time) assuming no response.
– a median case for floating oil exposure (area exposed at any time
during and after the spill)
– a “worst case” for shoreline oiling (97th percentile for shoreline
length oiled)
• Modeled response options
– Natural attenuation (no response action)
– Mechanical recovery – for oil fate demonstration (Mech)
– Mechanical recovery, in-situ burn, surface dispersant (MBSD)
– Subsea dispersant injection (SSDI), 100% treated beginning day
6, plus mechanical recovery, in-situ burn, surface dispersant
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• Comparative risk assessment workshop November 3 – 4 in Tampa
(Clean Gulf Conference)
• About 50 participants from TAC, industry, regulators and academia
• Review of the approach and results
• Breakout groups structured to facilitate discussions on:
• comparative risks of response strategies for the 2 scenarios,
• whether subsea injection of dispersants contributes to reducing the
overall impacts in the scenarios relative to other response strategies
• critical information needs.
Communications Efforts
•
•
•
•
•
•
External technical advisory
committees
Workshops
Factsheets
Newsletters
Peer-reviewed scientific
literature
Conferences
Website:
http://www.oilspillprevention.org

Industry has conducted extensive dispersants-focused
research building on decades of prior knowledge

API D3 program generated valuable scientific data on
various aspects of subsea dispersant injection

Results to date support the use of subsea dispersant
injection as a primary spill response tool
Subsea Dispersants – D3
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