Quantitative Description of the Selected Features of Silurian-Ordovician Shale Gas Petroleum System in Poland

The Baltic-Podlasie-Lublin Basin is located in the western margin of the East-European Craton. Potential area for shale gas exploration includes 55000km2.The stratigraphic profile are distinguished shale formations, that are a potential source of hydrocarbons, both conventional and unconventional. For the unconventional deposits it is lowermost Llandovery in the Baltic Basin, and Wenlock in the Lublin Basin. The Llandovery claystones and siltstones generally reveal fair to good oil-source rock potential. Locally it is very good to excellent. The measured organic carbon content (TOC) varies from 0.02 to 10.2 wt.%. The Wenlock strata show generally fair source rock parameters ( Figure 2A ). The TOC content is lower than in the Llandovery and do not exceed 1.5 wt.%, with median 0.7 wt.%. In the Lower Silurian strata oil-prone Type-II kerogen is present, deposited in anoxic and sub-oxic conditions. The maturity of the Lower Silurian strata, shown that the organic matter reveals wide range of thermal maturity, from initial phase of the “oil window” up to the overmature phase. Generally, the maturity increases in south-west direction. The numerical modelling reveal that the early phase of “oil window” was initiated in the beginning of Devonian, both in the Baltic Basin and Lublin Basin. The generation process was commenced in the early Carboniferous and continued until post-Carboniferous inversion.

3D static modelling, completed in the middle part of Baltic Basin, on PGNiG concession “Wejherowo”, performed in the potentially productive series revealed moderately favourable reservoir and geomechanical properties. The most promising complexes are in the investigation area claystones of Caradoc (Sasin Formation) and bituminous claystones of the Llandovery (Jantar Member). Other Ordovician and Silurian deposits in the central part of the Baltic Basin do not display relevant porosity, brittleness or/and TOC content. The result of these modelling is also more detailed structural and tectonic framework, different than it was assumed in the past.