A Review of the Relationship Between the Characteristics of Spilled Oil and Dispersant Effectiveness

Abstract

The effectiveness of a particular chemical dispersant is usually determined by various laboratory tests. Such laboratory performance cannot always be replicated in the field. The physical and chemical aspects of the actually spilled oil influence dispersant performance in a manner that usually cannot be extrapolated from the laboratory tests. Some of the important parameters discussed in this paper are the geometry, viscosity, and lens effect of the slick and the type of crude oil. Very thin slicks are sometimes not truly dispersed but are collected into a multiplicity of surface lenses by the penetration of the relatively large dispersant droplet. Heavily weathered and very viscous oil can resist contact with the more fluid dispersant and dispersant “roll-off” can ensue. An oil slick wherein 90% of the oil can be located in 10% of the area could result in overtreating some areas and undertreating others. The composition of the crude oil and its emulsion-forming tendency influence dispersant effectiveness regardless of other physical properties such as viscosity. This influence is more extensively discussed because of the unique effect of the crude oil composition on dispersant effectiveness.