BASIC STUDY REVEALS HOW DIFFERENT CRUDE OILS INFLUENCE DISPERSANT PERFORMANCE

Abstract

ABSTRACT Previous research has shown that crude oils contain various amounts of indigenous surface active agents that stabilize water-in-oil emulsions. It is also known that crude oils stabilize such emulsions to different extents. One aspect of the study was to investigate the relationship between the emulsion forming tendency of the various crude oils and the level of performance of a chemical dispersant on the particular crude oil. The results of the extensive laboratory test program indicated that dispersant effectiveness is a function of both dispersant type and the specific crude oil. However, there is no apparent correlation between the degree of emulsion-forming tendency of the crude oil, which is a function of the indigenous surfactant content, and effectiveness. A “clean” hydrocarbon, tetradecane (C14), was also tested in order to evaluate the absence of any indigenous surfactants on performance. It was found that tetradecane exhibited a higher level of effectiveness compared to the crude oils for each of the dispersants tested. In essence, the indigenous surfactants in the crude oil, in every instance, reduce dispersant effectiveness but to an unpredictable level. This is probably due to the fact that these agents present in crude oil promote a water-in-oil emulsion. Since the chemical dispersant is formulated to produce an oil-in-water dispersion, the interference of these crude oil surfactants is apparent. Hence, tetradecane would be an ideal test oil since the degree of dispersion of tetradecane by a particular dispersant represents the maximum dispersion effectiveness for that product. In order to establish more definitively the role of the indigenous surfactants, this surfactant phase was successfully separated from nine crude oils representative of different emulsion forming tendencies. It was found that the amount of surfactant residue extracted from the crude oil did correlate with the emulsion forming tendency of the crude oil. Finally, the above separated surfactant residue was added to tetradecane at the same concentrations as in the respective crude oil. As expected, in every instance, the surfactant residue decreased dispersant performance compared to “pure” tetradecane.