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Dispersant Effectiveness, In-Situ Droplet Size Distribution, and Numerical Modeling to Assess Subsurface Dispersant Injection as a Deepwater Blowout Oil Spill Response Option

Office/Division Program
Project Number
Research Initiation Date (Award Date)
Research Performing Activity
U.S. Environmental Protection Agency (EPA) and Center for Offshore Oil, Gas and Energy Research Fisheries and Oceans Canada (COOGER, DFO)
Research Principal Investigator
Dr. Robyn Conmy
Research Contract Award Value

This project addressed the operational performance of subsurface injection of dispersants into deepwater blowouts by developing methods focused on oil transport after dispersant injection by researching the following:

  • Refine existing equipment, technologies, and methodologies for the assessment and monitoring of subsurface dispersant application by measuring dispersed oil concentration, fluorescence, and in-situ oil droplet size distribution.
  • Evaluate dispersion effectiveness (DE) as a function of oil type, oil release flow rate, and dispersant-to- oil ratio (DOR) for deepwater blowout spill response.
  • Model the particle size distribution of dispersed oil under high flow velocities in deepwater blowouts.
  • Integrate the new formulation on droplet size distribution with deepwater blowout models to study the effects of the new formulation on oil fate/transport models.
  • Study the effects of dispersant on the droplet size distribution.
  • Develop a formula to predict droplet size distribution and integrate it with a transport/behavior model component for oil released from deepwater blowouts.

The project used the above information to address three issues:

  • Performance evaluation of dispersants for subsurface injection into sub-sea blowouts.
  • Tracking, modeling, and predicting the movement and spread of the deepwater plume and oil surfacing from deepwater blowouts.
  • Evaluating the influence of dispersant applications in reducing the concentration of volatile organic compounds emanating from the water surface.
Latest progress update

This project has been completed.

Some key findings from this work include:

  • Addition of either Corexit 9500 or Finasol OSR 52 chemical dispersants to the test oils decreased the Volume Mean Diameter (VMD) and shifted the Droplet Size Distribution (DSD) to smaller droplets. In general, Corexit 9500 produced smaller droplets compared to Finasol OSR 52.
  • Dispersions created without chemical dispersants or with a Dispersant‐to‐oil ratio (DOR) = 1:200 yielded VMD larger than 70 μm. Dispersions created with DOR = 1:20 yielded VMD between 2.5 to 70 μm size. This suggests that produced droplets from a DOR = 1:20 dispersant injection would likely remain dispersed in the presence of mixing energy.
  • Particle size analyses (LISST) near the injection release exhibited larger VMD compared to those generated further downstream from release in the tank indicating a shift from larger to smaller droplets within the plume for the lighter oils. This effect was not always observed with the heavier oil.
  • Water temperature did not appear to influence the DSD or VMD for lighter crude oil. However, a temperature effect was observed on the Total Particle Concentration (TPC), where lower temperatures were coincident with fewer particles dispersed within the plume for a given volume of oil injected.
  • VOC air monitoring was conducted above the tank during experiments. High VOC concentrations in the air were usually accompanied by higher BTEX concentrations in the water. For all oils tested, the addition of chemical dispersants (DOR = 1:20) resulted in a reduction in VOC concentrations compared to experiments without dispersant near the jet release location.
  • For experiments conducted at water temperatures less than 5 °C, particle size data from the LISST analyzers appears problematic. Although 5 °C is within the operating temperature of the LISST (manufacturer manual), additional testing of the cold water temperature limits of the sensor is recommended.
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