The influence of asphaltenes subfractions on the stability of crude oil model emulsions

Abstract

O petróleo é produzido na forma de emulsão água em óleo e os asfaltenos são considerados os principais responsáveis pela estabilização dessas emulsões. O objetivo deste trabalho foi avaliar a influência de diferentes frações asfaltênicas sobre a estabilidade de emulsões modelo de petróleo (salmoura em asfaltenos/tolueno) e sobre a eficiência de desemulsificantes. A estabilidade das emulsões foi acompanhada pelo ensaio de garrafa, com e sem a adição de desemulsificante. Os resultados mostram que a amostra de asfaltenos com larga distribuição de polaridade promove maior estabilidade da emulsão do que a amostra com distribuição mais estreita e polaridade intermediária. Além disso, a eficiência do desemulsificante na separação das emulsões está diretamente relacionada à estabilidade original da emulsão. Resultados de tensão interfacial evidenciaram a eficiência de deslocamento dos asfaltenos pelos tensoativos desemulsificantes, o que ocorreu com maior eficiência para as emulsões contendo frações de asfaltenos com distribuição estreita e polaridade intermediária.Crude oil is produced as water-in-oil emulsion, and asphaltenes have been considered the main responsible by their stabilization. The aim of this work was to evaluate the influence of the asphaltenes subfractions on the stability of petroleum model emulsions and on the efficiency of demulsifiers. Model water-in-oil emulsions were prepared: aqueous phase of brine and oil phase of asphaltenes in toluene. Different asphaltenes fractions were used. The emulsions' stability was assessed by the bottle test, with and without adding demulsifier. The results show that a sample of asphaltenes with broad polarity distribution promotes greater emulsion stability than a sample with narrow distribution and intermediate polarity. Besides this, the efficiency of demulsifiers in separating the emulsions is directly related to the original stability of the emulsion. Measurements of the interfacial tension revealed the efficiency of displacement of the asphaltenes by the demulsifiers, which occurred more efficiently for the emulsions containing asphaltenes fractions with narrow distribution and intermediate polarity.

Flocculation of Asphaltenes by Polymers: Influence of Polymer Solubility Conditions

“…The percentage of fraction A-C7I removed from the solution was significantly higher (∼70%) than that of A-C5I. This is coherent with the fact that fraction A-C5I is more stable than C7I due to the wider polarity distribution of its molecules, ,,,, and also because the polymer, with polar character, interacts preferentially with the more polar asphaltene molecules, indicating that the most likely action mechanism was adsorption of the asphaltenes on the polymers.…”

Alkanes Induced Asphaltene Precipitation Studies at High Pressure and Temperature in the Presence of Argon

“…The stability of crude oil in relation to asphaltene precipitation is one of the key factors for the development of petroleum fields as well as the design of the basic production facilities required for flow assurance. Moreover, asphaltenes are a class of molecules responsible for crude oil emulsion stabilization. − The thermodynamic conditions for asphaltene precipitation are conveniently determined through depressurization tests of live oil samples at pressures ( p ) and temperatures ( T ) consistent with the values prevailing for these parameters along the production process …”

Machine learning approach for predicting crude oil stability based on NMR spectroscopy

“…During petroleum processing, asphaltenes may form aggregates and precipitates, leading to serious problems in production, transportation and storage. The stability of asphaltenes in crude oils and petroleum products is one of the major challenges in petroleum industry, since there is no existing single method to determine stability of all oil fractions [6][7][8][9].…”