Composition of hydrocarbons-biomarkers of bitumoids of different-aged deposits of the Timan-Pechora and Volga-Ural oil and gas provinces

The study presents the results of hydrocarbon biomarker analysis in bitumoids extracted from Middle Devonian Eifelian rocks of the Yarega field and Permian-Carboniferous deposits of the Usinsk field in the Timan-Pechora petroleum province. It also examines bitumoids from Upper Permian Ufimian rocks of the Ashalcha and Mordovo-Karmal fields in the Volga-Ural petroleum province using a comprehensive geochemical approach. The analyzed biomarker group includes normal and isoprenoid alkanes, aromatic compounds, and cyclic isoprenoids such as steranes and triterpanes. Key geochemical parameters were determined on the basis of paraffinic, aromatic, sterane, and hopane hydrocarbons. A comparative analysis revealed similar sedimentary environments and a consistent type of original organic matter across the studied deposits. This suggests a marine origin of the original organic material, which accumulated and underwent diagenetic transformation under reducing conditions. The thermal maturity of the organic matter corresponds to the main phase of oil generation.