Hydrocarbon generation/expulsion modelling of the lower Paleozoic potential source rocks in the Gryfice and Kolobrzeg blocks (NW Poland)

Abstract

The lower Paleozoic source rocks in the offshore part of the Gryfice and Kolobrzeg blocks (NW Poland) were studied through geochemical data and numerical modelling. The geochemical study revealed a presence of effective source rocks in Caradocian strata, but with low hydrocarbon potential. The remaining lower Paleozoic source rock horizons were not documented by core samples. The timing of hydrocarbon generation and expulsion was modelled for the K1-1/86 and L2-1/87 boreholes located in the Gryfice and Kolobrzeg blocks, respectively. 1-D and 2-D modelling indicated that in the Kolobrzeg Block the onset of petroleum generation occurred at the end of the Silurian and the beginning of the Devonian. Source rocks in the Gryfice Block reached the early stage of oil generation at the beginning of the Permian and generation processes were completed by the end of the Triassic. Migration of hydrocarbons from source rocks began in the Carboniferous in both the Gryfice and Kolobrzeg blocks and lasted to the end of the Mesozoic. During hydrocarbon migration, an intensive dispersion process was observed, caused by leaking along the fault planes. The modelling revealed that hydrocarbons may have accumulated in Devonian reservoirs. The lack of any discovered accumulations could be the result of hydrocarbon dispersion caused by tectonic deformation and intense vertical fault block movements.