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• Parameters measured across various oil types: 
• Trials across range of Crudes and Fuel oils 
• 8+ dispersant types 
• Range of sea energy conditions 
• Range of Dispersant Oil Ratios (DOR’s) 
• Gives us a good indication of likely effectiveness for incident response. 
• Further details of individual trials can be provided by the UK MCA. 
And specifically: The 2003 UK Sea Trials 
The 2003 UK sea trials were funded by UK MCA and were carried out in the southern North 
Sea off Southwold in Suffolk. AEA Technology together with MCA devised the trials pro 
gramme in order to explore the factors which most influence the success or otherwise of dis 
persants as a countermeasure to oil spills. 
Figure 10.2: Picture from UK sea trials 
The ability to disperse spilled oils at sea depends on several factors, including oil properties, 
prevailing sea-state and the treatment rate of oil spill dispersant applied to the oil. 
We knew that oil spill dispersants function by allowing a high proportion of the spilled oil vol 
ume to be converted by cresting wave action into very small oil droplets that are permanently 
dispersed. Oil spill dispersants do this because the surfactants that they contain are capable 
of causing a very large decrease in the oil / water interfacial tension (IFT). IFT (or surface 
free energy) is caused by the dissimilarity between the polar nature of the molecules of water 
and the non-polar nature of the hydrocarbon molecules of oil. 
The trials sought to look closely at the effect of oil viscosity. In the case of low viscosity oils, it 
is the IFT that provides the main barrier to dispersion and the application of dispersants can 
overcome this barrier. The dispersant-enhanced dispersion then proceeds much more rapid 
ly, and to a greater extent, than natural dispersion. In the case of higher viscosity oils, such 
as FIFOs (Fleavy Fuel Oils) and highly weathered crude oils, the high viscosity exhibited by 
the oil, or the emulsified oil, is the major barrier than must be overcome by the dispersant, if 
the oil is to be dispersed. The high viscosity of a fuel oil or an emulsified crude oil can pre 
vent dispersion in two ways: 
(i) The high viscosity of the oil may prevent the dispersant from penetrating into the oil 
before it is washed off and away into the sea by wave action. Dispersants are only 
effective if the surfactants that they contain can contact the oil / water interface from 
within the oil. 
(ii) The oil may exhibit a high enough viscosity, or is accompanied by an elastic com 
ponent, that makes the oil capable of physically resisting the disruptive shearing