Abstract
The 2010 Deepwater Horizon oil spill highlighted the need for better understanding the interaction of dispersants and crude oil during high-pressure releases. This report summarizes a study to assess the operational performance of subsurface injection dispersant use on high-pressure releases within a flume tank. Dispersion experiments were conducted using South Louisiana Crude, Alaskan North Slope Crude and Intermediate Fuel Oil 120 oils, with Corexit 9500 and Finasol OSR 52 dispersants and four dispersant-to-oil ratios (DOR 0, 1:20, 1:100, 1:200) at warm and cold temperatures. In situ plume dispersion was monitored for particle concentration and Droplet Size Distribution (DSD; LISST-100X), and fluorescence intensity. Samples were collected for Total Petroleum Hydrocarbons and Benzene-TolueneEthylbenzene-Xylene concentrations. Empirical data was subsequently used as input variables to refine numerical models of droplet size formation (VDROP-J, JETLAG and Modified Weber Number). This project also generated a fluorescence library of 25 oil types to expand community knowledge base on optical signatures as a function of oil type. In general, the addition of dispersant decreased the oil Volume Mean Diameter (VMD), creating smaller droplets. Dispersions at DOR =1:20 yielded VMD <70 µm and exhibited bimodal DSD, suggesting that produced droplets would likely remain dispersed in the presence of mixing energy. Water temperature did not appear to influence the droplets for lighter crude oils. DSD results suggest a separation of particles within the plume. In situ fluorescence was found to be a reliable proxy for oil concentration. These findings have implications for the fate and transport of oil plumes-both for spill response monitoring and numerical modeling