1D modelling of hydrocarbon generation and expulsion from Oligocene Menilite source rocks in the San and Stryi rivers region (Polish and Ukrainian Carpathians)

Based on geochemical data of the Oligocene Menilite Shales in the Boryslav–Pokuttya, Skole (Skyba), Silesian (Krosno) and Dukla units in the Carpathians, between Krosno and Styi towns, 1D modelling of generation and expulsion processes of hydrocarbons has been carried out. These strata are characterized by mostly high organic matter content, the total organic carbon (TOC) content reaching up to 26 wt.%. The highest hydrocarbon potential was recorded in the Boryslav–Pokuttya and Skole units. Organic matter in the Skole (Skyba) Unit is immature; in turn, in the Boryslav–Pokuttya, Silesian (Krosno) and Dukla units it is mature enough for generating hydrocarbons. Results of the modelling reveal that during the deposition of flysch in all the above mentioned Outer Carpathian units the Menilite source rocks did not reach a level of thermal maturity high enough to generate hydrocarbons. Conditions of hydrocarbon generation were obtained in the thrusting stage of the Outer Carpathians. In general, the process of hydrocarbon generation began at depths of less than 2 km in the Polish part, and about 4 km in the Ukrainian part. The kerogen transformation level reached from 10% to to complete transformation as in the Suche Rzeki IG 1 well.The results of the modelling of hydrocarbon generation and expulsion from the source rocks of all the units reveal that the highest maturity and the highest generation potential were obtained by the Menilite Shales in the Silesian and Dukla units