Organic matter contained in Lower Paleozoic rocks of the East European Craton is highly variable in terms of thermal maturity which encompasses a full range of hydrocarbon generation conditions.
Shale sediments of the eastern Baltic Syneclize (NE Poland) are the least altered rocks. They contain immature organic matter which is at an early liquid hydrocarbon generation stage. Thermal maturities of Lower Paleozoic sediments markedly increase towards the marginal zone of the East European Craton. In top Silurian intervals of NE Poland they reach the main and late oil generation phases.
In the central and marginal SE zone of the Craton, top Silurian formations are in the main gas window. Moreover, thermal maturities of the shale rocks tend to increase with burial depth. Bottom Silurian beds in the marginal portion of the Craton in NW Poland and the lowest penetrated Silurian beds in SE marginal area of the Craton contain organic matter in the main gas window or, locally, at the post-maturity stage.
It should be noted at this point that local positive thermal anomalies that potentially could trigger hydrocarbon generation processes have been reported from Poland's NW and SE regions.
authors: Izabella Grotek, Marcin Janas