Recent improvements in optimizing use of dispersants as a cost-effective oil spill countermeasure technique

Abstract

Recent improvements in optimizing use of dispersants as a cost-effective oil spill countermeasure technique. Abstract Several oil spill incidents during recent years have demonstrated that the physico-chemical properties of spilled oil and the effectiveness of available combat methods are, in addition to the prevailing environmental and weather conditions, key factors that determine the consequences of an oil spill. Pre-spill analyses of the feasibility and effectiveness of different response strategies, such as mechanical recovery and dispersants, for actual oils under various environmental conditions should therefore be an essential part of any oil spill contingency planning to optimize the overall "Net Environmental Benefit" of a combat operation. During the four-year research program ESCOST ("ESSO-SINTEF Coastal Oil Spill Treatment Program"), significant improvements have been made in oil spill combat methods and in tools for use in contingency planning and decision-making during oil spill operations. This paper will present an overview of the main findings obtained with respect to oil weathering and oil spill dispersant treatment during this research program, including:–New methodology for systematic investigations of the weathering properties of oils at sea–Development of high performance dispersant formulations for weathered and emulsified oils–Improvements in dispersant application techniques and applications procedures /strategies–Development of dynamic oil spill simulation model tools for use in designing more optimal and cost-effective oil spill contingency solutions. The results from the ESCOST program have been obtained through systematic laboratory and meso-scale basin studies, and numerical model developments. In addition, two successful full-scale controlled field trials have been conducted in the North Sea during 1994 and 1995. The results from the full-scale field trials have been used in verifying the laboratory experiments, calibrating the numerical model tools, and to investigate the effectiveness of different oil spill dispersant application techniques under realistic oil spill scenarios. The findings obtained in the ESCOST program have formed a foundation for the present effort among oil companies and authorities in implementing more operational, optimal dimensioned and cost-effective oil spill contingency for offshore platforms, refineries and oil terminals in Norway. Background for the ESCOST Program: Oil spills in recent years have demonstrated the high level of public concern related to the potential effects caused by oil spills. These spills have also reconfirmed the importance of having model tools available both for predicting the different oils behavior and to assess the feasibility and effectiveness of different countermeasure techniques such as mechanical recovery or dispersants. The behavior of spilled crude oils and refined oil products depends on the prevailing conditions (e.g. temperature, sea-state, currents) and on the chemical composition of the oil. Large variations in crude oil properties cause them to behave differently when spilled at sea. The crude spilled at the "Braer" incident in the Shetlands had e.g. a low content of waxes and asphaltenes which are important compounds for stabilizing water-in-oil (w/o) emulsions that usually are formed on the sea surface. This, combined with violent weather conditions, resulted in consequences that were much less severe than might have been expected. Almost all of the 84,000 tons of the spilled crude oil was naturally dispersed. P. 899