Abstract
Permian rocks occur over more than 80% of the Polish territory and, in middle Poland, they occur at considerable depth, from 2 to 6 km. The Early Permian was a period of long-lasting intensive volcanic activity. The Late Permian and Zechstein began with desert deposition which was followed by evaporitic deposition of a shallow epicontinental sea. The middle Polish trough (MPT) constituted the central part of the late Permian basin and was the site of the earliest and longest deposition with the most intensive periodical subsidence not compensated by sedimentation. Subsidence rate and syndepositional faulting substantially controlled the paleogeographic pattern. The final structure of the oil and gas fields was caused by late diagenesis and Upper Cretaceous structural remodeling. The upper Rotliegendes have the biggest natural gas fields. Reservoir rocks are sandstone and sandstones interfingering with conglomerates in tectonically active zones. The most promising areas for hydrocarbon exploration are the marginal parts of the basin (UPL) and the contact zone between MPT and the adjacent platforms. In the central part of the basin, the most promising are sandstone complexes on elevated tectonic blocks. Zechstein hydrocarbon fields occur in carbonate horizons of the first three cycles (PZ1, PZ2, and PZ3). Inmore » some areas, the Zechstein limestones (Cal), constitute the natural gas reservoir. Main dolomite (Ca2), oil, gas, and condensate fields are connected with the carbonate platform or its slope. Source rocks for oil occur in the Ca2 basinal facies or in the deeper parts of the platform-type lagoons. Oil migration is short and lateral, from either the basin or lagoon, toward the carbonate platform. Gas in Ca2 derived from the sub-Zechstein basement and migrated vertically along fault zones. The most prospective areas are reservoir horizons of the carbonate platform occurring in the near source rocks. The play dolomite Ca3 is not very promising.« less
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