Fundamentals of asphaltene phase behavior in heavy oil and tar sands
- Rice Univ., Houston, TX (United States)
- INTEVEP, Caracas (Venezuela)
As a continuation and update of work presented at the 5th UNITAR International Conference on Heavy Crude and Tar Sands, this presentation addresses the phase behavior of asphaltenes in terms of traditional thermodynamics of mixtures and in terms of interfacial phenomena known to be an integral part of the problem. Recent experimental studies have demonstrated the pressure effect on apparent reverse micelle behavior of asphaltenes in petroleum fluids. Published results have shown that certain commercial surfactants have been effective in ameliorating the problem of asphaltene precipitation in crude oils, and in solubilizing asphaltenes deposited in porous media. These recent observations correspond well with the concepts advanced in our previous studies. Phase behavior of asphaltenes in heavy crude and in tar sands is again addressed from the fundamental point of view, at the molecular level, to interpret observed behavior and to provide a logical means of forecasting expected behavior in these fluids under many different physical and chemical conditions. Interactions between resins and asphaltenes, in the presence of heavy crude or tar sands, do not follow classical thermodynamics, at least, not faithfully. Resins tend to interact as amphiphiles between the asphaltene-free material and the asphaltenes. Resins may be in solution with the asphaltene-free material; however, resins are adsorbed at the surface of the asphaltene aggregations, forming micelles or other amphiphilic structures. Phase behavior of asphaltenes, therefore, depends upon the thermodynamic equilibrium of resins distributed between the asphaltenes and the asphaltene-free material. In crude oils, resins may form solutions which reasonably conform to the Modified Regular Solution Theory, as described previously. At the asphaltene-resin interface, adsorption can be described in terms of classical theories of adsorption and/or similar association mechanisms for interfacial phenomena.
- OSTI ID:
- 269537
- Report Number(s):
- CONF-9502114--Vol.1
- Country of Publication:
- United States
- Language:
- English
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