Source Rock Evaluation and Petroleum Processes in the Lower Palaeozoic Strata (Onshore of the Polish Baltic Basin)

The study area comprising the western part of the Polish Baltic Basin is a most important exploration target in Poland in the unconventional resources aspect. Geochemical analyses of 840 rock samples were used in this study. They represented all Lower Palaeozoic stratigraphic horizons. The investigations showed that the samples in whole study area represent active source rocks. The best source-rock parameters are observed in the Upper Cambrian - Tremadocian complex. The all investigated Lower Palaeozoic strata contain oil-prone, low-sulphur Type-II kerogen deposited under anoxic or sub-oxic conditions. The maturity of Lower Palaeozoic strata change from the initial phase of “oil window” in the northeastern part of the area to overmature stage in the southwestern part of analysed area. Numerical modelling of generation and expulsion of hydrocarbons indicates the source rocks reached the complete generation interval from early to late stage. The early stage was reached from the beginning of Devonian to the beginning of the Carboniferous. The main and final generation stages were reached during the middle Devonian – early Tournaisian time. The organic matter reached the transformation degree from several percent to the complete transformation.