| Abstrakt: |
The paper presents an analytical review of studies that discuss issues concerning the geochemistry of organic matter in Jurassic–Cretaceous rocks in the Arctic regions of Western Siberia and genetically related oils, gas condensates, and hydrocarbon gases. The Late Jurassic Bazhenov Formation and the coeval Golchikha (upper part) and Yanovstan (middle part) Formations are regarded as the major oil-source rocks in this region. Unlike the classic Bazhenov Formation in the central areas of Western Siberia, the Late Jurassic oil-source marine organic matter (OM) in the Arctic region is characterized by an admixture of terrestrial biomaterial and oxidizing conditions during diagenesis, with these features reflected in its composition of the OM and the related oils and gas condensates. These hydrocarbon fluids were accumulated mostly in Early Cretaceous rocks. The other oil-source rocks in the area are those of Early–Middle Jurassic formations enriched in mixed highly mature organic matter: the Zimnyaya, Sharapovo, Kiterbyut, Laida, and Malyshev. Oil and gas condensates generated in these formations were detected in the Middle Jurassic rocks (in the Yenisei–Khatanga area and in the eastern part of the Gydan Peninsula), and in the Jurassic and Cretaceous rocks (in the Yamal Peninsula and in the western Gydan Peninsula). Other rocks thought to have been able to generate oil in the area are the shale beds enriched in marine organic matter of the poorly studied Late Jurassic Sigov and Abalak Formations and the lower strata of the Early Cretaceous sedimentary sequences (Nizhnyaya Kheta, Shuratov, and Akh Formations). The almost whole Jurassic–Cretaceous rock complex is thought to be gas-producing. However, the main gas-generating rocks are thought to be those of Early–Middle Jurassic age and the Late Jurassic rocks with highly mature organic matter. The source of isotopically light dry gases of the Aptian–Albian–Cenomanian formations are reportedly the terrestrial (carbonaceous) organic matter in the Cretaceous rocks affected by early catagenic transformations. The contribution of the early catagenic gases to the gas potential of this region is debatable. Oil and gas generation centers in Arctic Western Siberia are localized in the most strongly subsided depression zones of the area and south of it. It should be noted that much published data on the geochemistry of organic matter are unsystematic and heterogeneous, and hence, detailed geochemical studies of the Jurassic–Cretaceous rocks of this area as a whole shall be carried out, with primarily focus on its northernmost parts. [ABSTRACT FROM AUTHOR] |
Full text from SpringerLink