Comparison of Organic Matter from Upper Jurassic Oil Shale of the East European Platform and the Bazhenov Formation by Molecular and Isotopic Data

The molecular and isotopic composition of an extract from the rocks of the Bazhenov Formation in the southeast part of Western Siberia, oils that are genetically related to this formation, and products of hydrous pyrolysis of the organic matter of oil shale (Middle Volgian) of the East European Platform were studied. Common features and differences in their molecular composition were shown. The carbon isotope composition for C₁₄–C₃₀n-alkanes was determined for the first time; a negative isotope anomaly was revealed for C₂₆n-alkane in all samples studied. It was concluded that in spite of the geographical distance, specific biota was revealed in the Volga Basin. This biota conditioned an isotopic indicator, which is genetically significant.     

Organic Matter of the Salt Sequence in the Southern Part of the Yakshinskoe Potassium–Magnesium Salt Deposit

Organic component in the Lower Permian salt sequence in the southern part of the Yakshinskoe deposit of the Upper Pechora potassium basin is represented by dispersed organic matter, liquid hydrocarbons in fluid inclusions in halite, as well as inclusions of bacterium, algae, spore and pollen of plants. Analysis of saturated and aromatic bitumen fractions from salts, halopelites, and clayey–silty interbeds revealed the presence of organic matter of type II and mixed type II–III. It is shown that the cover sequence and potassium bed from the southern part of the Yakshinskoe potassium–magnesium salt deposit contain autochthonous immature organic matter, whereas underlying rock salt and host rocks contain significant amount of immature allochthonous components. These migration hydrocarbons are likely immature condensates.     

Changes in the composition of bitumen extracts and chemical structure of kerogen during hydrous pyrolysis

The paper presents data on the composition of biomarkers from bitumen extracts and the chemical structure of kerogen from C_org-rich sedimentary rocks before and after hydrothermal treatment in an autoclave at 300°C. Samples selected for this study are kukersite and Ordovician Dictyonema shale from the Baltics, Domanik oil shale from the Ukhta region, Upper Permian brown coal from the Pre-Ural foredeep, carbonaceous shale from the Oxfordian horizon of the Russian plate, and Upper Jurassic oil shales from the Sysola oil shale bearing region. The rocks contain type I, II, III, and II-S kerogens. The highest yield of extractable bitumen is achieved for Type II-S kerogen, whereas Type III kerogen produces the lowest amount of bitumen. The stages of organic matter thermal maturation achieved during the experiments correspond to a transition from PC_2–3 to MC_1–2. The ¹³C NMR data on kerogen indicate that the aromatic structures of geopolymers underwent significant changes.     

Organic matter in Silurian rocks from the Chernov uplift

This study presents data on the composition of organic matter from the Late Silurian sediments of the Chernov uplift. These sediments are characterized by low C_org contents, which may reach 1–3% in individual layers. A relatively high thermal maturity of organic matter is confirmed by polycyclic biomarker distributions and Rock-Eval pyrolyisis data. Despite its higher thermal maturity level (T _max = 456°C), kerogen in carbonaceous shales from the Padymeityvis River exhibits good preservation of long-chain n-alkyl structures, which are readily identified in the ¹³C NMR spectra and by the molecular analysis of the kerogen pyrolysis products.     

Analysis and characterization of ash-free coals from the Pechora coal basin obtained by organic solvent extraction

Doklady Earth Sciences - The probability of obtaining of ash-free coal extracts, so-called “hyper-coals,” has been shown for coals of the Pechora basin for the first time. The ash...