OILSLICK and DIFF are Det Norske Veritas (DNV) tools for computing hydrocarbon (HC) concentrations in the water masses and for weathering studies. The two models may be run together or separately.
OILSLICK computes the behaviour and characteristics of an oil slick i.e. thickness, width and budgets for evaporated, dispersed and dissolved fractions (as function of the distance from discharge point) of HC, generated from a surface spill.
DIFF computes the HC concentrations in the water masses, following a surface or a subsurface release (blowout, see DNV’s model BLOW).
The composition of the HC is one of the input to OILSLICK. The HC are divided into 100 components of individual physical characteristics. In addition, the meteorological conditions (wind, temperature) have to be specified. For the computations of the concentrations in the sea, the vertical current velocity profile as well as the temperature and salinity profiles have to be given. DNV has ocean current models such as MURGOM to generate current input to OILSLICK/DIFF.
The following figure shows an oil slick budget modelled by OILSLICK.
The validity of the models are limited in elapsed time to 10 - 20 hours from release, giving typical distances validity up to 5 – 20 km from the release. Processes not included in the present version are emulsification, biological degradation and photochemical processes.
The results from OILSLICK may be used as input to other DNV oil spill models handling large-scale oil drift and ocean flows such as OILTRAJ and SHOREDRIFT.
OILSLICK / DIFF have been used in several Norwegian fjords. The oil spill results have mainly been used in environmental risk assessments and weathering studies.
The following figure shows how the hydrocarbon concentrations distribute in the water masses. It shows the concentrations in a vertical section downstream the centre of the release modelled by DIFF.
Reference:
- Concentration of oil in water generated from surface spills, Report No. 93-3674, Det Norske Veritas, 1993.
