The environmental impacts of an oil spill and the attendant response applied for ecological restoration would mostly depend on the conditions of the spill, nature of the area, quantity and type of oil released, meteorological and climatological factors, as well as the effectiveness of response techniques. The Indonesian government and operators have been considering best ways of shielding the environment and their reputation from spill hazards, in cognizance of the region's high sensitivity and vulnerability.

This paper thus undertakes a risk assessment for the potential environmental effects of possible spillage of medium light crude pumped to the Floating Storage and Offloading (FSO) terminal installed to handle production and bulk distribution of oil produced from a green oilfield offshore Indonesia. GNOME and ADIOS were deployed to forecast the trajectory and fate of oil spilled from the FSO during loading operations to ocean-going tankers, respectively. Key environmental data obtained from ESI maps were built into the models to yield desired results.

The likely trajectory of oil released from the FSO as depicted by GNOME results for nine days after the spill and the contact probabilities show that 5,200 barrels of the oil would beach on the ninth day. Response efforts must thus be effected before this occurs. The results from ADIOS were captured for both winter and summer conditions; indicating that more spilled oil would remain after a 5-day period, if it occurs during winter, than would be obtained for a spill during summer. This implies less complicated cleanup operations in summer than in winter. However, since the oil is medium light, the lighter fractions would readily evaporate out, leaving behind heavier oily residues that may form tar balls with the submarine sediments and sink to the sea bottom or arrive at the beach, as shown by GNOME.

Subsequent Net Environmental Benefits Analysis suggests that dispersants would not be a good response option due to their toxicity to the ecologically sensitive ecosystem. It is thus recommended to contain imminent spills using dykes and booms within a few hours of occurrence, before further dispersion and beaching. Subsequent in-situ burning would then enable all the hydrocarbons and most other contaminants present to burn off, thus protecting the shoreline and submarine resources. The study will guide spill responders and serve as a basis for future oil spill contingency plans (OSCPs) in the field and others within the Southeast Asian hydrocarbon provinces.

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