brought together what we thought and what has been shown
As part of an ongoing investigation into the stability of waterin many literature studies to be the primary contributors to in-crude oil emulsions, model oils have been utilized to further the solubility state of asphaltenes which in turn should have probe the effects of crude solvency as well as specific resin-asphala pronounced effect on the stability of these emulsions. tene interactions on emulsion stability. These model oils were con-Asphaltenes are in fact reported to stabilize emulsions to structed by dissolving varying amounts of resins and/or asphalthe greatest extent when they are at or near the point of tenes in a mixture of heptane and toluene. The resins and asphalprecipitation (2 -4 ). It is also well known that the solvency tenes used in this study were isolated from four different crude state of petroleum asphaltenes is primarily governed by their types-Arab Berri (AB), Arab Heavy (AH), Alaska North Slope interactions with the resins and the surrounding crude me-(ANS), and San Joaquin Valley (SJV) -and characterized in a previous study using heptane precipitation of the asphaltenes fol-dium ( 5-13 ). In our conceptual model, we proposed that lowed by an extrographic separation of the resins from silica gel. these interactions are dominated and determined by the Asphaltenes dissolved in heptol at concentrations of just 0.5% were availability of solvating resins, the extent of hydrogen bondshown to generate emulsions which were even more stable than ing between the asphaltenes and resins, and the aromatic those generated from their respective whole crude oils. Some types solvency of the resins and of the saturates and aromatics in of resins (e.g., from AH and SJV) also demonstrated an ability to the crude medium itself. We then proceeded to test the stabilize emulsions although these resin-stabilized emulsions were sensitivity of these interactions on the stability of emulsions considerably less stable than those prepared with asphaltenes. The produced from four different crude oils -Arab Berri (AB) , primary factors governing the stability of these model emulsions Arab Heavy (AH) , Alaska North Slope (ANS ), and San were the aromaticity of the crude medium (as controlled by the Joaquin Valley (SJV ). In this previous study on whole heptane:toluene ratio), the concentration of asphaltenes, and the crude oils, we were able to show to a limited extent that availability of solvating resins in the oil (i.e., the resin/asphaltene or R/A ratio). The model emulsions were the most stable when crude solvency parameters such as the R/ A ratio, the aromathe crude medium was 30-40% toluene and in many cases at small ticity of the solvating crude components, and the polar func-R/A ratios (i.e., R/A °1). This strongly supports the theory that tionality of the resins and asphaltenes play an important asphaltenes are the most effective in stabilizing emulsions when role in determining emulsion stability.
they are near the point of incipient precipitation. The types of resins
In this study, we have continued our investigation of the and asphaltenes used to construct these model oils also played a stability of water-in-crude-oil emulsions by harnessing the role in determining the resultant emulsion stability which indicates utility of so-called model oils. These model oils were conthe importance of specific resin-asphaltene interactions. The interstructed from the resins and asphaltenes isolated from these facially active components that stabilized these model systems were same four crude oils and were then emulsified with water the most polar and/or condensed portions of the resin and asphalto gain further insight into the effects of changes in crude tene fractions as determined by elemental and neutron activation solvency and resin-asphaltene interactions on the resultant analyses. All of these results point to the significance of the solubility state of the asphaltenes in determining the emulsifying potential emulsion stability. One of the goals of studying these model of these crude oils. ᭧ 1997 Academic Press emulsions was to show that the resin and asphaltene fractions are capable of stabilizing water-in-oil emulsions even without other stabilizers such as inorganic solids and waxes. But