Characterization of Asphaltene Deposits by Using Mass Spectrometry and Raman Spectroscopy

Abstract

Crude oil deposition in oil transfer pipelines and bore wells afflicts many oil reservoirs. Asphaltenes play a major role in this process because of their tendency to precipitate in pipelines upon changes in temperature and/or pressure. Asphaltenes are defined by their lack of solubility in n-alkane solvents, which means that they likely contain many compounds that do not actively contribute to the deposition of crude oil in pipelines. The preponderance of studies in the literature have focused on asphaltenes derived from crude oil, whereas far fewer investigations have focused on asphaltenes derived from oil deposits. In this study, structural parameters of oil-deposit asphaltenes were examined using Raman spectroscopy and tandem mass spectrometry and compared to results reported previously for petroleum asphaltenes. On the basis of D1 and G band intensities in the Raman spectrum of oil-deposit asphaltenes, the average aromatic sheet size of these molecules was 21.0 A, slightly larger than earlier values...