Abstract
Gas chromatography/mass spectrometry (GC/MS) can only analyze volatile molecular compounds, and it has limitations when applied to determine the complex components of crude oils and hydrocarbon source rocks. Based on Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and GC/MS analyses, the molecular compositions of NSO compounds in extracts from the Permian Dalong Formation, Sichuan Basin and the Permian Lucaogou Formation, Junggar Basin in China were compared. Analyses of types of heteroatoms present (S1, S2, S3, OS, OS2, O2S, NS, and NOS compounds) suggest that marine shales from the Dalong Formation are mainly composed of carboxylic acids (O2 compounds) with a high abundance of fatty acids, indicating a marine phytoplankton organic source. However, lacustrine shales from the Lucaogou Formation are dominated by pyrrolic compounds (N1 compounds) with abundant dibenzocarbazole. It suggests that the organic source materials may be derived from lower aquatic organisms and lacustrine algae. Overall, FT-ICR-MS has potential for applications in analyses and determination of depositional environments and organic sources in petroleum geology.
Highlights
Crude oils are composed of complex hydrocarbons and nonhydrocarbons
Gas chromatography/mass spectrometry (GC/MS) can only analyze volatile molecular compounds, and it has limitations when applied to determine the complex components of crude oils and hydrocarbon source rocks
The Dalong Formation shale has a large content of nalkanes with the highest content of nC15
Summary
Crude oils are composed of complex hydrocarbons and nonhydrocarbons. Traditionally, column chromatography is used to separate the aliphatic hydrocarbons, aromatics, resins, and asphaltenes. Aliphatic and aromatic hydrocarbons are analyzed by gas chromatography (GC), GC– MS, and GC along with coupled tandem mass spectrometry. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) is widely used to determine the differences of polar compounds in crude oils from different districts with various maturity and biodegradation degrees (Qian et al 2001; Hughey et al 2004, 2007). This research is to investigate the NSO compounds of shale extracts from the Dalong Formation in the Sichuan Basin (Fu et al 2010; Liang et al 2009; Xia et al 2010) and the Lucaogou Formation in the Junggar Basin, China (Zhao et al 1994; Peng et al 2011) using negative ion electrospray ionization (ESI) coupled with FT-ICR-MS, and compare their differences and similarities from analyses of the composition of the acidic and neutral nitrogen heteroatom compounds
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