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EN
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.
EN
Maturity modelling was carried out using basin and petroleum system modelling (BPSM) software in the lithologic sections of 17 wells of the Upper Silesian Coal Basin (Poland). The best fit between calculated and measured vitrinite reflectance (VR), porosity and density data was obtained by applying a thickness of eroded sedimentary overburden from 1700 m in the east to 4500 m in the west and relatively low to moderate heat flow values during the maximum late Carboniferous burial. These heat flow values were in the range 50-71 mW/m2
EN
Raman spectroscopy and vitrinite reflectance measurements of dispersed organic matter from Carboniferous shales in boreholes in the northern part of the Intra-Sudetic Basin were used for thermal history reconstruction. Microscopic investigations have shown that the organic matter is dominated by the vitrinite maceral group. In analysed samples, organic matter shows a varied degree of thermal alteration determined by the mean random vitrinite reflectance (VRo) ranging from 0.72% to 3.80%. Mean apparent maximum vitrinite reflectance (R’max) values reached 4.98%. The full width at half maximum of D1 and G bands in Raman spectra are well-correlated with mean VRo and R’max. Thermal maturity in the boreholes shows a regular increase with depth. Geological data combined with Raman spectroscopy and mean vitrinite reflectance results indicate that the analysed Carboniferous strata reached maximum paleotemperatures from c. 110 to c. 265°C. The regional paleogeothermal gradient in the late Paleozoic was c. 80°C/km. The Variscan heating event presumably caused a major coalification process of organic matter. The Carboniferous–Permian magmatic activity must have contributed to high heat flow, adding to the effect of sedimentary burial on the thermal maturity.
EN
Three-dimensional, structural and parametric numerical modelling was applied to unravel the unconventional hydrocarbon potential of a W-dipping, Lower Palaeozoic mudrock succession, which subcrops for some 700 km in the Baltic, Podlasie and Lublin basins across the SW margin of East European Craton in Poland. Input data comprised structural and thickness maps of Ordovician and Silurian strata and the results of thermal maturity (mean vitrinite-equivalent reflectance, % Ro) and total organic carbon (TOC, % wt.) modelling. A new, spatial interpretation of vitrinite-reflectance variability indicates that the regional, W-increasing thermal maturity pattern breaks into a series of domains, bounded by abrupt maturity variations. In total, 14 tectono-thermal domains were recognised and their boundaries traced to known and inferred faults, mostly of NW‒SE and NE‒SW orientations. On the basis of a combination of thermal maturity and total organic carbon levels (0.6% > Ro<2.4%, and TOC >1.5% wt.), good-quality, unconventional reservoirs can be expected in the Sasino Formation (Caradoc) and Jantar Formation (early Llandovery) in the central and western Baltic Basin. The Jantar Formation also is likely to be prospective in the western Podlasie Basin. Marginal-quality reservoirs may occur in the Sasino and Jantar formations within the Podlasie and Lublin basins and in the Pasłęk Formation (late Llandovery) across all basins. Poor- to moderate-quality, unconventional reservoirs could be present in the Pelplin Formation (Wenlock) in the Lublin and southern Podlasie basins. In spite of a considerable hydrocarbon loss during multiphase basin inversion, the Ordovician and Silurian mudrocks still contain huge quantities of dispersed gas. Successful exploitation of it would require the adoption of advanced fracking methods.Lower Palaeozoic, shale gas, shale oil, Baltic Basin, Lublin-Podlasie Basin, total organic carbon, thermal maturity, structural-parametric model.
EN
Thermal maturity modelling was carried out in over sixty wells along the SW margin of the East European Craton (EEC). The burial and thermal history modelling of the EEC, using thermochronological data, allowed the construction of burial history maps showing its geological development in the Phanerozoic. These results have proved that the Ordovician and Silurian source rocks occurring at the SW margin of the EEC reached a maximum palaeotemperature in the Palaeozoic, mainly during Devonian-Carboniferous time and at the latest during the Silurian in the most westerly part of this margin, along the Teisseyre-Tornquist Zone. In Mesozoic and Cainozoic time, the Ordovician and Silurian strata generally were subjected to cooling or to very minor heating, certainly below the Variscan level. The maximum burial and maximum temperature of the Ediacaran-Lower Palaeozoic strata were reached during the Early Carboniferous in the Baltic Basin and during the Late Carboniferous in the Lublin area, and even in the Early Permian in the SE corner of the Lublin Basin. Thus, the main period of maturation of organic matter and hydrocarbon generation in the Ordovician and Silurian source rocks was in the Late Palaeozoic (mainly Devonian-Carboniferous) and in the westernmost zone along the Teisseyre-Tornquist line at the end of the Silurian.
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