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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
The aim of this study was to use the structural restoration technique to verify the correctness of the structural and palaeothickness maps created during the BLUE GAS Project. On the basis of well data as well as refined structural and palaeothickness maps of Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic and Cretaceous horizons, a cross-section running across the Baltic Basin, the Mazury High and the Podlasie Basin was created. During the restoration process, the effects of compaction and fault activity were removed sequentially. The amount of erosion was estimated on the basis of the corrected palaeothickness maps. The resulting restoration is geologically reasonable and therefore both the structural and palaeothickness maps should be regarded as reliable. The reconstruction also allowed reproduction of the initial geometry and thickness of the Cambrian–Devonian strata and the recognition of three main episodes in the evolution of the sedimentary cover of this part of the East European Craton. The first episode was related to the deposition of the Lower Palaeozoic (up to the Lower Devonian) sedimentary complex on the relatively flat surface of the East European Craton edge. During the second episode, lasting most probably to the Permian, the Baltic and Podlasie Basins subsided significantly. The amount of subsidence was much higher in the Podlasie Basin. The third episode is related to the deposition of the almost flat-lying Mesozoic–Cainozoic complex.
EN
In this work, 1-D numerical modelling of petroleum generation and expulsion processes in the Upper Ordovician and Lower Silurian source rocks was carried out in over sixty wells along the SW margin of the East European Craton (EEC) in Poland. Lower Palaeozoic sediments were subjected to rapid burial in the Palaeozoic and then were uplifted in several phases, but with the predominance of the late Variscan tectonic inversion. The thermal maturity of organic matter in the Lower Palaeozoic strata indicates the advancement of the generation processes from the phase of low-temperature thermogenic processes in the NE part of the Baltic and Podlasie-Lublin basins to the overmature stage along the zone adjacent to the Teisseyre-Tornquist Zone (TTZ). The results of modelling of generation and expulsion show that these processes took place mainly in the Devonian and Carboniferous periods and in the westernmost part (along the TTZ), even in the latest Silurian. The hydrocarbon expulsion took place with a small - delay after generation. During the Mesozoic and Cainozoic, generation processes practically were not resumed or intensified. Nevertheless, it was found that zones with an increased shale gas potential can occur only in a relatively narrow belt on the SW slope of the EEC, parallel to the edge of the TTZ. The most promising seem to be Caradocian, Llandovery and the Wenlock between the Lębork IG-1 and Kościerzyna IG-1 wells in the Baltic Basin, and the Wenlock source rocks in the Podlasie-Lublin Basin between the Okuniew IG-1, Łopiennik IG-1 and Narol IG-1 wells. Most of the hydrocarbons were subjected to expulsion and possible migration. As a result, there was a large dispersion of the hydrocarbons generated. The chance of preservation of these hydrocarbons in the source rocks is small.
EN
The paper presents a multi-phase and multi-stage methodology of 3D structural-parametric modelling and mapping that has been applied during implementation of the GAZGEOLMOD project. The core of the applied processing workflows is a 3D geological model constructed in Petrel, which functions as a spatial database for all kinds of geological models. The first phase of the workflow comprised an extended process of database project building that was very intensive at the beginning of the project and continued to its end. The second phase of processing consisted of a complex process of mapping and structural modelling that is performed in 8 stages, allowing for iterative improvements of model resolution. During the realization of stages 1 to 7, processing was run independently for the Baltic (BB), Podlasie (PB) and Lublin Basins (LB). The workflow included the following stages: (1) unification and digitization of published and on file analogue and digital, structural maps; (2) preliminary reinterpretation, including adjustment to stratigraphy data acquired from archives; (3) adjusting the maps to the primary results of seismic interpretation, mainly from archival data; (4) digitization and gridding of pre-existing palaeothickness maps and updates of them with data from boreholes completed after 2009; the reinterpretation of the palaeothickness maps into contemporary thickness maps; (5) elaboration of the primary structural 3D models for the three basins; (6) increasing of the stratigraphic resolution of models up to the rank of the geological epoch for Ordovician–Silurian strata; (7) conversion of basin-scale structural models into a 2D grid, and their merging into platform-scale surfaces, resulting in 45 structural and thickness maps; finally, they were adjusted to the results of seismic interpretation and sedimentological studies, obtained in the project; and (8) completion of the resulting structural models for each of the basins and for the entire Polish part of the East European Craton in several different versions. In the third phase of processing, parametric models of vitrinite reflectance (Ro) and Total Organic Carbon (TOC) were estimated.
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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