Formation and behaviour of thin oil films and evaluation of response methods including HSE

Oil spill incidents, which lead to thin oil films, are becoming an increased concern for oil spill contingency planning in Norway. This development is caused by increased production of condensates and light crude oils characterized by high quantities of light organic compounds and the risk for subsea blowouts on the Norwegian Continental Shelf. Furthermore, there is an increased transport of condensates, light crude oils and refined oil products along the Norwegian coast. It has been assumed that the oil films formed by such oil spills may be too thin for effective recovery by traditional mechanical response techniques. Thin oil films in this context are defined as oil films having initial thicknesses from 5 µm up to 200 -300 microns. Thicknesses below 5 µm do not likely produce significant environmental effects on biota (e.g. sea birds) and are considered not to be combatable by any known response technology. In this project, comprehensive laboratory studies were performed focusing on behaviour of thin oil films in both closed and open exposure systems under controlled and reproducible conditions, for different condensates and light crude oils. In addition, oil spill response options for thin oil films were tested. The results have been important for understanding processes like emulsification and solidification of such thin oil films and have been used as input for development of the methodology for establishing recommended oil spill response strategies for thin oil films. Refers to SINTEF scientific reports Thin Oil Films Properties and behaviour at sea. Laboratory studies and oil weathering predictions by Ramstad et al., 2016 (Unrestricted), and Project Recommendations for Response to Oil Spills from Condensates and Light crude oils (Unrestricted) (Singsaas et al., 2017). The laboratory testing of response concepts was performed to optimize new approach for high-capacity water flushing as a basis for constructing a prototype bow-mounted flushing boom. The 2016 full-scale field trial contributed to testing of the prototype and was a first verification of the water flushing technology. The development and customizing of the concept was conducted as a separate part of NOFOs technology program Oljevern 2015, SINTEF report Mekanisk dispergering av tynne oljefilmer (Sørheim et al., 2017). The prototypes were developed and constructed in cooperation with Jason Engineering AS. The field trial was conducted in cooperation with NOFO and Norwegian Coastal Administration (NCA) in June 2016. Both NOFO and NCA contributed financially to a successful field trial. The evaluation of response strategies based on findings from this experimental field trial are summarized in SINTEF scientific report (Daling et al., 2017) Full-scale field testing of thin oil films from releases of light crude oil at sea. Findings from the field trial are also published in AMOP proceeding conference paper (Daling et al., 2017) Light Crude Oil Slicks Behaviour and Effect of Response Options during Full-scale Field Experiments. Presentation from the full-scale field trial were given at two international conferences in 2017 (GOMRI and AMOP). In this project, we aimed to implement refined sub-models in the oil trajectory-modelling tool. The temperature and salinity profiles can now be imported into the SINTEF's OSCAR (Oil spill contingency And Response) model from netCDF format, and categorization of surface oil film thicknesses are available in the currently official release version of OSCAR. Controlled spreading experiments using waxy model oils were conducted to study oils with different spreading properties on the sea surface. A yield stress-inhibited spreading sub-model was developed and implemented in a research version. A manuscript Spreading of waxy oils on calm water from this work has been published (Brönner et al., 2018). A PhD study, titled Air Monitoring of Volatile Organic Compounds with Respect to Risk of Human Exposure was conducted in this project to assess the potential exposure to volatile compounds during response operations of condensates and light crude oils spilled at sea. The PhD study included laboratory experiments to measure the air concentration of BTEX, naphthalene and n-hexane evaporated from a thin oil film. A focus of the PhD study was the potential for human exposure to chemical hazards during response operations. During the field trial, measurements of Total Volatile Organic Compounds (TVOC) was performed on two oil types. The data published indicate that concentrations of volatile (benzene) and hazard components are decreasing rapidly after an oil spill, Gjesteland et al., 2017 Oil Spill Field Trial at Sea: Measurements of Benzene Exposure. Biological uptake of benzene was measured by collecting urine samples of the participants before and after work shift (Gjesteland et al., 2018) Biomonitoring of Benzene and Effect of Wearing Respirators during an Oil Spill Field Trial at Sea.

This project will generate new knowledge about the behaviour of thin oil films, created by condensates and light crude oils, in oil spill situations. The topic is interesting both for the oil industry and national and international governmental response a gencies (e.g. NCA, Bonn Agreement and EMSA) because the results will form the basis for safe and effective handling of thin oil films from both offshore and coastal spill incidents. The studies on human exposure will give valuable information about the he alth risk for personnel involved in response actions and give the industry a possibility to reduce the probability for short-term and long-term health injuries.