Accidental oil spills may cause severe marine pollution, with serious impacts to wildlife and their habitats. The fate of oil spilled at sea depends upon multiple factors, such as the released quantity, the oil properties, the meteo-marine conditions. The identification of the hazard associated to offshore oil spills is thus fundamental in order to reduce or mitigate their impact on the different environmental compartments of the sea. The use of indicators represents a widespread approach in offshore risk management to capture and effectively communicate complex issues, as the hazards due to accidental events. This paper presents a methodology based on Key Performance Indicators (KPIs) to assess the environmental hazards caused by oil leakages from offshore oil & gas production facilities. Three different levels of KPIs are defined, based on data and resource availability. The first level of KPIs is associated to the spill features, the second one is based on the inventory of the release and the third type considers the area of the floating oil slick. A case study regarding an offshore oil platform in the Mediterranean Sea is introduced in order to demonstrate the potential of the proposed approach. The results show the potential of KPIs in representing the hazards of different oil spill scenarios, thus offering a tool for hazard screening, as a preliminary step of more detailed oil spill risk assessment studies and contingency planning activities.
The offshore oil & gas industry recognizes an extreme importance to the management of the risk related to oil spills deriving from its activities. Directive 2013/30/EU on the safety of offshore oil & gas operations  introduced strict criteria related to the environmental performance of offshore facilities, also requiring operators to demonstrate the ability of covering liabilities from major accidents. However, the Directive does not propose or require the application of any specific methodological tool to assess the environmental consequences associated with potential oil spills. Oil releases are a form of marine pollution which can result in both immediate and long-term environmental damage to different environmental compartments, i.e. sea surface, water column, sea bottom, shoreline. The 2010 BP Deepwater Horizon accident in the Gulf of Mexico caused the largest offshore spill in the USA history, with extensive contamination of surface water, water column, deep-sea corals and benthos, nearshore and coastal ecosystems . Despite massive clean-up efforts following major oil spills, historical evidence shows that long-term effects of embryonic exposure to hydrocarbons may be expected for several years in fish along the water column, in addition to the immediate mortality of seabirds and benthic invertebrates on oiled shores . Clearly, the severity of environmental damages caused by oil depends on multi-faceted factors related not only to the quantity and type of oil spilled, but also to the vulnerability of wildlife in the area and even to the ambient conditions during and after the accident . Therefore, identification of the hazard associated to offshore oil dispersion is fundamental to all aspects of oil spill risk assessment and oil spill contingency planning.