AAPG ACE 2018

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Applications of Multivariate Curve Resolution to the Interpretation of Geochemical and Mineralogical Data Relevant to Petroleum Systems

Abstract

Multivariate curve resolution (MCR) is widely applied to a variety of data types, including complex spectra and chromatograms containing multiple components. It is particularly useful when examining large numbers of samples whose interpretation is time-consuming or non-obvious. MCR analysis can delineate subtle features, such as overlapping peaks, and can support initial interpretations to guide further examination. Results from methods like X-ray diffraction and nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and X-ray absorption near-edge structure (XANES) spectroscopies can be decomposed to reveal pure phases or co-varying combinations of mineral or organic components. Pyrograms from programmed pyrolysis can also be examined by this method. For example, MCR can be used to separate multiple Gaussian components in S2 peaks from source rock pyrograms. These peaks can be related to petrographic analysis where multiple organic matter types are present in mudrocks. In this study, samples from a wide range of petroleum systems were examined using a suite of geochemical and mineralogical analyses. Standard interpretation approaches were combined with MCR analysis to assess different applications. Pure- and mixed-mineral components were obtained via MCR analysis of X-ray diffractograms; these components are consistent with those obtained by pattern-fitting approaches, with component weights that are in agreement with semi-quantitative results from Rietveld analysis. Applying MCR analysis to programmed pyrolysis pyrograms yielded components with different Tmax values and S2 responses, which indicates the presence of different organic matter types; this is consistent with petrographic and geochemical characterization. Additional tests using NMR, XANES, and FTIR datasets provided information on the distribution of organic moiety types present in oils, bitumens, and kerogens. These results show the utility of MCR for preliminary or alternative interpretation of petroleum geochemical analysis.