The method we apply is based on many years of experience. It is recognised internationally and has been published. Laboratory data is used as input to numerical models such as the SINTEF Oil Weathering Model (OWM) and the SINTEF Oil Spill Contingency and Response (OSCAR) model. These models predict factors such as physical changes to the weathering characteristics of oils, oil trajectory, and oil behaviour both on the sea surface and in the water column.
The laboratory utilises the Laboratory Information Management System (LIMS) in order to meet stringent requirements linked to the quality of documentation and reporting.
In order to isolate the effects of the different weathering processes (such as evaporation and emulsification), oil weathering is carried out using a systematic, step-wise procedure first developed, and later modified, at SINTEF. Our laboratory offers research facilities at both bench- and meso-scales (a test basin) for the study of phenomena such as the weathering characteristics of oils, and their dispersibility at different temperatures (using a climate room).
SINTEF keeps a unique stock of oils and various residues, taken mainly from the Norwegian shelf, but also from other parts of the world, as well as a variety of oil products such as diesel and bunker oils.
We offer physical-chemical analyses and the characterisation of oils and residues:
The step-wise weathering of oils and oil products, including simple distillation (topping) of fresh oil to 150 °C, 200 °C and 250 °C+ (residue)
Water content determinations using the Karl Fischer instrument
- Pour point
- Asphalt and wax content in oils
- Viscosity and rheological measurements
- Interfacial Tension Tests (IFTs – spinning drop and pendant drop tensiometry)
- Chemical characterisation using gas chromatography methods:
- WAF (Water Accommodated Fraction). Chemical and toxicological characterisation of the WAF of raw oils and oil products.
Characterisation of the emulsifying properties of oils:
Oil-in-water emulsification is the most important weathering process that causes oils to remain at the water surface. Properties such as water uptake capability, rates of water uptake, and the stability of emulsions formed at the water surface following an oil discharge, vary among different oil types and depend on the chemical composition of the oil. Some oils are able to take up as much as 80 vol. % water, while others exhibit significantly lower uptake capabilities. In the laboratory we calculate a so-called "t1/2" value that estimates the time in hours it takes for an oil to emulsify half of its maximum water content.
When an oil spill occurs, the oil may be a relatively thin, low-viscosity fluid. However, after only a few hours it can be transformed into a thick and highly viscous water-in-oil emulsion that may be three or four times its original volume. Knowledge of an oil's emulsifying properties thus has a major influence on the selection of spill-combatting strategies and the equipment used in spill mitigation operations. The oil laboratory characterises emulsions in terms of their water uptake and physical properties, stability, the effect of demulsifiers and emulsion dispersibility (see the separate item below).
This can be summarised as follows:
- Production of emulsions with different oil and water fractions
- Kinetics (rates of water uptake)
- Viscosity of emulsions with different oil and water fractions
The use of a dispersal agent may promote oil-in-water dispersal because the agent reduces the interface tension between the oil and water, causing the formation of small droplets that are more easily mixed down in the water column. This reduces the volume of oil/emulsion on the sea surface.
The oil laboratory carries out dispersibility tests using some of the most recognised methods including IFP, MNS and WSL. We refer also to the method described in Norwegian statutory regulations. Test results provide data on which to base selection of the most suitable dispersal agent and optimal dosage for the oil in question when combatting a marine spill, as well as estimates of the "time window" within which the agent should be used. Moreover, we offer a simple field procedure (FET test) that provides a measurement of dispersibility in the field/at sea, and during meso-scale testing in the basin at SINTEF.