Kerogen and crude oil asphaltenes are compositionally similar and it has been proposed that characterization of asphaltenes can be useful for oil-oil and oil-source rock correlations in petroleum systems. Thermal stress has also been shown to affect moiety distributions in kerogens and asphaltenes in similar ways, suggesting that the correlation between kerogen and asphaltene composition may be preserved through catagenesis. A comparison of the distribution of functional groups between kerogens and associated asphaltenes by infrared spectroscopy can be useful in correlation studies of petroleum resource basins. Bonds formed by the principal elemental components of petroleum (CHNOS) can be observed in the infrared, with the most sensitive bonds being those in aliphatic (C-H), carbonyl (C=O), and aromatic (C=C) structures. Attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy is rapid, non-destructive, and requires very little sample preparation, making it a more economical method for assessing large sample sets relative to other methods such as gas chromatography-mass spectrometry to characterize biomarkers. Applying chemometric and multivariate statistical methods to FTIR spectral data allows for the modeling and assessment of moiety distributions via computational algorithms rather than by simple visual interpretation. In this study, immature kerogens and asphaltenes isolated from expelled oil pyrolysates generated by hydrous pyrolysis experiments over a range of temperatures (270 to 365 °C) were analyzed using ATR-FTIR. Samples containing Type I lacustrine (freshwater and brackish-saline), Type II marine (including low- and high-sulfur samples), and Type III (coal) organic matter were analyzed. The spectral results were examined using cluster and principal component analysis and partial least squares regression methods. The results show that asphaltene moiety distributions determined by FTIR are useful for relating petroleum families and for linking expelled oils to particular source rocks.

Correlating crude oil and kerogen properties to asphaltene fractions using infrared spectroscopy and chemometrics

253rd National Meeting (2017)

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