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Kerogen can release both liquid and gaseous hydrocarbons during thermal maturation. In this study, the maturation and hydrocarbon generation of a low-maturity type II kerogen were simulated via tem...

Simulations of aerobic biodegradation have been widely employed to investigate the mechanisms of crude oil biodegradation in geological environments. In this study, a simulated biodegradation experiment was performed with crude oil under aerobic conditions, in which n-alkanes were nearly depleted, thus providing an opportunity to study the biodegradation mechanisms of n-alkanes in crude oils. The sequences of biodegraded oils with a slight to moderate degree of biodegradation were characterized by negative-ion electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and gas chromatography (GC). Semiquantitative results on the molecular compositions of heteroatom classes were obtained by coinjection of internal standards. The biodegradation mechanisms for n-alkanes and n-fatty acids, as well as some other heteroatomic compounds, are discussed. Evidence from FT-ICR MS and GC analyses of biodegraded oils indicates that n-alkanes can be progressively biodegraded to n-fatty ac...

The compositions of crude oils can vary significantly during thermal maturation through cracking and aromatization. In this study, an immature high sulfur crude oil was pyrolyzed in a closed gold-tube system with heating rates of 20 °C/h and 2 °C/h, respectively, to simulate the thermal maturation process of crude oil. The molecular compositions of heteroatom-containing compounds in crude oil were investigated by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) while the impact of thermal maturation on migration and maturity geochemical parameters were investigated by gas chromatography–mass spectrometry (GC-MS). Based on the analysis of pyrolysis products, the compositional variations of heteroatom-containing aromatic compounds and the validity of the aromatic geochemical parameters during thermal maturation were investigated. When the equivalent vitrinite reflectance value (Easy %Ro) was greater than ca. 0.85, alkyl chain cracking was the major reaction and led to the producing of...

Five heavily biodegraded tar sand bitumens from an oil column were separated into maltene and asphaltene fractions for analysis by negative-ion electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). These bitumens have an identical source, which have experienced a natural sequence of biodegradation. The polar NSO compounds in maltene fractions contain O1, S1O1, O2, S1O2, S2O2, O3, S1O3, O4, S1O4, N1, N1O1, N1O2, N1S1, and S1 classes, while the polar NSO compounds in asphaltene fractions contain O1, S1O1, S2O1, O2, S1O2, S2O2, O3, S1O3, S2O3, O4, S1O4, S2O4, O5, S1O5, S2O5, O6, N1, N1O1, N1O2, N1O3, N1S1, and N2 classes. Polar NSO compounds with stronger molecular polarity and larger molecular weight are readily fractionated into asphaltene fractions. The O2 class is prevalent in polar NSO compounds of both maltene and asphaltene fractions of all bitumen samples. The N1 class in maltene fractions is dominated by compounds with DBE values of 9, 10, 12 and 13, while the N...