Hydrocarbon generation modelling in the Permian and Triassic strata of the Polish Basin: implications for hydrocarbon potential assessment

Hydrocarbon generation in the Zechstein Main Dolomite and Upper Triassic potential source rocks of the Polish Basin was investigated by 1-D thermal maturity modelling in 90 boreholes across the basin. This identified major zones potentially worthy of further exploration efforts. The maximum burial depth of the Zechstein Main Dolomite and Upper Triassic reached >5 km during the Late Cretaceous leading to maximum thermal maturity of organic matter. Hydrocarbon generation development reveals considerable differences between particular zones of the Zechstein Main Dolomite and Upper Triassic. The kerogen transformation ratio (TR) in the Zechstein Main Dolomite reached values approaching 100% along the basin axis. The TR in the Upper Triassic source rocks is generally lower than in the Zechstein Main Dolomite due to lesser burial. The Upper Triassic source rocks have the highest TR values (>50%) along the basin axis, in the area between boreholes Piła IG 1 and Piotrków Trybunalski IG 1, with the most pronounced zone in the Krośniewice Trough (i.e., between the Krośniewice IG 1 and Budziszewice IG 1 boreholes), where the TR reached >90%. The Zechstein Main Dolomite and Upper Triassic entered the oil window in the Late Triassic to Early–Middle Jurassic, respectively. Hydrocarbon generation continued until the Late Cretaceous, and was completed during tectonic inversion of the basin.