Poster Session - IFP Invited Poster

Amphiphilic Compounds of Heavy Oils: Influence of their Interfacial Properties on Emulsion Stability

G. Alvarez (1), J. Argillier (1), D. Langevin (2)

(1) Institut Français du Pétrole, 1-4 avenue de Bois Préau, 92852 Rueil-Malmaison Cedex, France

(2) Laboratoire de Physique des Solides, Université Paris-Sud, bâtiment 510, 91405 Orsay Cedex, France

Emulsions of heavy oil and water can be encountered at many stages during production, transportation and processing of crude oils and in many locations such as in hydrocarbon reservoirs, well bores, surface facilities, transportation systems and refineries. A good knowledge of petroleum emulsions is necessary for controlling and improving processes at all stages. The complexity of petroleum emulsions comes from the oil composition in terms of surface active molecules contained in the crude, such as naphthenic acids and asphaltenes.

Here, we present a study of dynamic interfacial tension and rheology of interfaces between water and either diluted crude oil or a model oil (toluene) in which asphaltenes, resins and model naphthenic acids are dissolved. We show that different parameters such as model naphthenic acid/asphaltene ratio, concentration, ageing of the interface, pH and salinity of the aqueous phase have a strong influence on interfacial properties and emulsion stability. Small-angle neutrons scattering (SANS) measurements, in which the structure of the interfacial layer is obtained, are described as well as UV-VIS experiments that allowed us to determine the adsorbed asphaltene amount at the interface.

The microscopic properties of the different interfaces and the stability of the corresponding macroscopic emulsions have been shown to be well correlated. The influence of lower molecular weight surface-active species, such naphthenic acids has been investigated, and interactions between asphaltenes and these acids were detected. The results obtained on model emulsions and model oil/water interfaces were found to be very helpful in order to explain and predict the behavior of heavy crude oil emulsions.

Key Words: asphaltenes, naphthenic acids, heavy oils, emulsions, stability, interfacial properties.