Laboratory testing of dispersant effectiveness at high pressures

Oil spills remain a serious environmental problem, and can have significant economic and ecological consequences. Despite the advantages, accidental deep-sea oil releases during offshore exploration or production activities are of particular concern as the potential for such incidents increases significantly as we move to deeper waters. Dispersants are important mitigation tools as they have the capability to disperse the oil into a cloud of tiny oil droplets that can be readily degraded by hydrocarbon degraders if suitable environmental conditions prevail. In the case of an offshore incident, the dispersant is injected near the point of crude oil release so that dispersion is more effective. Given that our experience with subsea dispersant use is limited, the effect of pressure on the effectiveness of the dispersant has not been established, and hence, the composition and amount of dispersant to be injected has not been optimized. For typical surface oil spills, dispersant effectiveness is experimentally measured under laboratory conditions by the US-Environmental Protection Agency (EPA) baffled flask test, which was later adapted as ASTM standard method F3251. Despite its extended use, this test cannot be used for testing dispersants at elevated pressures. In order to see whether pressure affects dispersant effectiveness, we developed a simple laboratory test protocol using a high-pressure reactor (HPR). In addition, the effectiveness of five commercially available dispersants (COREXIT (TM) EC9500A, COREXIT (TM) EC9500B and COREXIT (TM) EC9527A, Marichem (TM), and Oiler 60) applied to a dead light crude oil has been determined at various pressures for the first time, and these values have been related to the standard baffled flask test (BFT) at atmospheric pressure. It is shown that pressure increase adversely affects dispersant effectiveness; however, the effect varies from a few percent to nearly a 50% decrease for a pressure increase of 100 bar depending on the particular dispersant used.

Automated summary

Oil spills are a significant environmental problem with economic and ecological consequences. Dispersants can help mitigate these spills by breaking up the oil into smaller droplets. This study examines the effectiveness of five commercial dispersants under different pressures, and finds that increasing pressure negatively affects their effectiveness.