BURIAL AND THERMAL HISTORY AND HYDROCARBON GENERATION MODELLING OF THE LOWER PALAEOZOIC SOURCE ROCKS IN THE KRAKOW-RZESZOW AREA (SE POLAND)

Burial history, thermal maturity and timing of hydrocarbon generation were modelled for the Ordovician and Silurian source rocks in the basement of the Carpathian Foredeep. 1-D modelling was carried out for wells located in the area between Krakow and Rzeszow cities (SE Poland). The following wells were modelled: Bedzienica 2, Hermanowa 1, Nawsie 1, Nosowka 2 and 12, Pilzno 40, and Zawada 8K. The Ordovician and Silurian source rocks, containing oil-prone Type-II kerogen, are generally immature showing less than 0.5% reflectance of vitrinite-like macerals (R-o), in most of the Krakow-Rzeszow area and only in the eastern part the organic matter is early mature, reaching 0.7% equivalent R-o. The highest thermal maturity is found in the eastern part of the study area, near Rzeszow city, where the Lower Palaeozoic strata are buried to the greatest depth. Maturity modelling shows that the source rocks reached the initial phase of the "oil window" only in the eastern part of the area, whereas they are immature in the larger, western portion of the area. In addition, modelling indicates that the onset of petroleum generation started in the late Miocene, after the Outer Carpathian overthrust phase. The generation processes in the eastern part of the analysed area reached the main and late generation phase. The generated hydrocarbons were mostly expelled from the source rocks. In the western part of the study area the generation process has not been initialized.