Rise Velocity of Live-Oil Droplets in Deep-Sea Oil Spills

Resolving the dilemma of dispersant use for deep oil spill response

“…The rise velocity of an oil droplet is an increasing function of its diameter and degree of saturation with natural gas components [1,4,5]. For an intermediateviscosity black oil like Louisiana sweet crude (which has been used as a proxy for DWH studies), oil droplets smaller than approximately 70 μm can be rendered neutrally buoyant due to small-scale ocean turbulence [1].…”

“…A number of studies have conducted or summarized experimental approaches to estimate oil droplet sizes from scaled-down laboratory experiments, in test tanks, and, in one case, a field-scale experiment [1,12,13]. Laboratory experiments to assess oil droplet diameters have been undertaken in a small number of facilities: the SINTEF facilities in Norway, the OHMSETT tank in New Jersey, the Southwest Research Institute highpressure vessel in Texas, the high-pressure test facility at the Hamburg University of Technology in Germany [4,5,12] and in stirred sapphire cells at the University of Western Australia [11] and elsewhere. Extrapolating droplet behavior from these laboratory apparatus to ultra-deep field-scale conditions is complicated by a number of factors.…”

BP Gulf Science Data Reveals Ineffectual Subsea Dispersant Injection for the Macondo Blowout

“…As reported in Crespo-Medina et al 2014, the deep plume started to break down after July when the discharge stopped, with lower concentrations onward (green dots, Figure 2B). A clear gap in intermediate waters with background concentrations suggested acceleration of degassing droplets under decreasing pressure (Pesch et al, 2018) and/or biological consumption of this low molecular weight hydrocarbon category in the water column (Bagby et al, 2017).…”

“…Corexit 9500 is a powerful surfactant containing dioctyl sodium sulfosuccinate (DOSS) that lowers the interfacial tension between the oil and the water and enhances formation of neutrally buoyant micro-droplets (Wilson et al, 2015). This mechanism dictates that the enhanced dispersion increases the hydrocarbon content of the deep plume (Paris et al, 2012;Aman et al, 2015;Pesch et al, 2018), but DOSS could also increase the toxicity of the sequestered material (Kujawinski et al, 2011). Additionally, the amount of surfacing oil should slow, and sheens should be thinner, further downstream from the spill site (Socolofsky et al, 2015), which could help mitigate response efforts.…”

“…Additionally, the amount of surfacing oil should slow, and sheens should be thinner, further downstream from the spill site (Socolofsky et al, 2015), which could help mitigate response efforts. Indeed, the droplet size distribution (DSD) generated during subsea blowouts has a strong impact on their outcome since they dictate the oil rising speed (Paris et al, 2012;Pesch et al, 2018). Yet, little is known about the impacts of subsea dispersant injection (SSDI) on the transport of petroleum hydrocarbons and its tradeoffs, beyond modulating the extent of environmental contamination by decreasing natural degradation and increasing water column toxicity.…”