INSTABILITY FROM QUALITY AND QUANTITY OF ASPHALTENES (IQQA)

摘要

A new method for instability prediction based on the quality and quantity of fee asphaltenes (IQQA method) is presented. A simple description of solubility based on me interfacial tension together with a molecular vision of the surface tension allows to understand me low values of maltenes surface tension at the flocculation point. General stability of asphaltenes in me crude, far from flocculation, is explained considering the tendency to adopt the surface tension value of me medium to minimize the free energy of interaction. This property of the large asphaltene molecules, to change its surface tension to minimize me mterfacial tension with the media is reflected on me independence of the flocculation point with the asphaltene concentration. A traditional Heithaus experiment using Alfa methyl naphthalene (AMN) as solvent, and Hexadecane as precipitant, allows to obtain the Shell P value and the quality of asphaltenes at infinite dilution. These values together with density, weight fraction of asphaltenes, and the density of isolated asphaltenes allow to establish the general condition for stability: density of the crude's maltenes should be higher than critical density of crude's maltenes, which is the density below which me asphaltenes would precipitate. The mixture of crudes properties are calculated using the corresponding volumetric fraction and instability predicted. Some examples will be shown.