Application of a Regular Solution-Based Model to Asphaltene Precipitation from Live Oils

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• 作者：Asok Kumar Tharanivasan ; Harvey W. Yarranton ; Shawn D. Taylor
• 刊名：Energy & Fuels
• 出版年：2011
• 出版时间：February 17, 2011
• 年：2011
• 卷：25
• 期：2
• 页码：528-538
• 全文大小：979K
• 年卷期：v.25,no.2(February 17, 2011)
• ISSN：1520-5029

文摘

A previously developed regular solution approach was adapted to model asphaltene precipitation caused by compositional changes and depressurization. The model inputs are the mass fraction, molecular weight, density, and solubility parameters for each component. A Gulf of Mexico crude oil was characterized into components, and mass fractions were assigned on the basis of gas chromatographic and saturates, aromatics, resins, and asphaltenes (SARA) analysis. Densities for pentane plus and SARA fractions were obtained from published data. For lighter components, effective densities were determined from extrapolated n-alkane data. The density of the live oil from 80 to 120 掳C and pressures from 10 to 100 MPa was predicted to within the error of the data assuming ideal mixing. Solubility parameters of each component were determined as a function of the temperature and pressure. The only unknown was the average molar mass of the asphaltene nano-aggregates in the oil, which was used to fit the measured precipitation onset pressure data. The model successfully predicted asphaltene yield data below the onset pressure for the live oil as well as yields for the dead oil diluted with n-heptane. The results indicate that a common characterization can be used to model both solvent- and pressure-induced precipitation. However, the pressure-induced precipitation is very sensitive to the average aggregate molar mass. Thus, the predictive capability of this approach is limited.