The complexity of shale formation interpretation requires an accurate evaluation of a detailed petrophysical model in association with the analysis of the geomechanical properties. Mineralogy plays an important role in controlling shale’s mechanical properties, among which one of the most problematic parameters to establish is the Biot’s coefficient. Although, this parameter is necessary to determine the magnitude of the effective stresses acting in the reservoir, it is not included in the standard protocols used in Poland. This paper presents a comprehensive petrophysical and geomechanical evaluation of the unconventional reservoirs of lower Paleozoic age formation: lower Silurian and Ordovician deposits located in the onshore part of the Baltic Basin (Poland). In this study, the Biot’s coefficient from well-log data was calculated. Initially, a calibrated rock-physics model was derived to provide a set of relationships between the elastic and petrophysical properties. Based on an accurate, calibrated petrophysical model, the effective bulk modulus along with the Biot’s coefficient and horizontal stresses were calculated. Ultimately, the tectonic regime was determined. Using full-waveform sonic data analysis, the horizontal anisotropy was estimated. The directions of maximum and minimum horizontal stress were established based on several X-tended Range Micro Imager images of breakout structures and drilling-induced fractures.

We have developed a Lower Palaeozoic petroleum systems analysis in the selected zones of the Polish section of the Baltic Basin (onshore and offshore), which we carried out to assess the potential of shale rock formations as unconventional reservoirs. The areas of the Baltic Basin, which we analyzed represent a diversity of shale formations burial depths and thus different advancement of sediments compaction and organic matter transformation. Methods of dynamic petroleum systems modeling were applied with a 3D modeling workflow (PetroMod suite software). We considered an extensive array of data, including results of geochemical and petrophysical laboratory measurements, geophysical borehole data and, in selected locations — 3D seismic data. Five potentially perspective shale rock intervals (Silurian [2], Ordovician [2], and Upper Cambrian [1]) are identified and interpreted in terms of their geochemical and petrophysical properties. We calibrated the petroleum system models in terms of proper reproduction of diagenetic processes (pore pressure and porosity), thermal conditions (vitrinite reflectance, temperature), and kerogen kinetic model (organic matter transformation ratio, types of hydrocarbons generated). The results of the petroleum system simulations reveal that for the predominant part of the analyzed area, the achieved level of kerogen thermal maturity determines the generation of liquid hydrocarbons, which results in the present-day saturation of shale formations mainly with crude oil. We concluded that the highest generation yields as well as present-day hydrocarbons in place are observed for Ordovician Sasino Formation (onshore and offshore), Silurian/Llandovery Jantar member (onshore), and Upper Cambrian (alum shales) formation. Furthermore, a significant variation in the mass/volumes of accumulated hydrocarbons is observed within each of the shale formations being considered.

The main aim of the article is to determine the possibility of a more detailed seismic interpretation in the autochthonous Miocene formations on the example of a 3D seismic survey from the Carpathian Foredeep area, based on the comprehensive analysis of well logs. The seismic survey located in the central part of the Carpathian Foredeep was selected for the study. This zone is characterized by the presence of natural gas accumulation in various types of traps. Four boreholes in which formation tests were conducted within the Miocene sediments were selected for the detailed interpretation of the well logs. An important element of the study was the seismic-to-well tie based on available measurements of vertical seismic profiling. The quantitative interpretation of well data was the basis for the distinction of several lithofacial complexes of diverse lithology, reservoir parameters, or the type of reservoir media saturation in the profile of each of the analysed wells. Water and hydrocarbon saturations were estimated based on Montaron's theory. With the defined seismic signature, it was possible to interpret seismic horizons away from the wells. Selected seismic attributes were used during the interpretation and analysis of the seismic image. There was a fairly high correlation between the well logs interpretation and the seismic record. Major lithological changes, thicker claystone interbeds within mudstone, or heterolithic deposits, as well as zones of significant changes in reservoir properties and the type of reservoir media saturation can be interpreted in the seismic image. In contrast, mudstone or heterolithic complexes of a large thickness (about hundreds of meters) in the seismic image are usually characterized by a monotonous low amplitude record and a significantly smaller continuity of reflections. The zones saturated with gas or gas and brine, documented in the analysed wells by the results of formation tests, usually can be identified on the basis of the seismic record. Due to the large variation of lithology and a substantial variability of individual parameters, it is not possible to reliably indicate in the seismic data which of the analysed objects are saturated with natural gas, and which with gas and brine. The results of well logs and integrated seismic interpretation allowed to obtain the complete picture of the Miocene siliciclastic formations diversity in the studied region, as well as a more accurate determination of reservoir properties and reservoir fluid saturation. The series of fine-grained sediments (mainly mudstone or heterolithic) in the lower part of the Miocene profile, within which several prospects were interpreted, was determined as the most interesting for hydrocarbon exploration.

Artykuł przedstawia wyniki przeprowadzonych prac z zakresu interpretacji profilowań otworowych i modelowania geologicznego w wybranych strefach basenu bałtyckiego. Analizowano cechy formacji łupkowych determinujące ich perspektywiczność jako niekonwencjonalnych złóż węglowodorów. Ocenie poddawano zakresy wartości parametrów petrofizycznych i geochemicznych, jak również ich przestrzenną zmienność. Analizowano profile otworowe i modele geologiczne w rejonie Opalino-Lubocino, Wysina i Borcza oraz strefy struktur B8 i B21 na Morzu Bałtyckim. Przedmiotem zainteresowania były takie parametry interwałów łupkowych jak: miąższość, zawartość materii organicznej TOC, porowatość, nasycenie mediami złożowymi, skład mineralogiczny oraz zasoby geologiczne węglowodorów nasycających formacje łupkowe. Przedstawiono możliwości wykorzystywania wyników interpretacji otworowych oraz modelowania geologicznego w zagadnieniach identyfikacji stref o najkorzystniejszych właściwościach skał oraz oceny potencjału zasobowego formacji łupkowych. Słowa kluczowe: formacje łupkowe, modelowanie geologiczne 3D, basen bałtycki. Comparative analysis of shale formations in selected areas of the Baltic Basin based on well data interpretation and 3D geological modeling The article presents the results of borehole data interpretation and geological modeling in selected areas of the Baltic Basin. Properties of shale formations which define its prospectiveness as unconventional reservoirs were analyzed. Petrophysical and geochemical properties values, as well as their spatial variability were assessed. Wellbore profiles and geological models were developed and analyzed for the following areas: Opalino-Lubocino, Wysin-Borcz and B8 and B21 structures, offshore Baltic Sea. Parameters such as thickness of the shale intervals, organic matter content TOC, porosity, saturation, mineralogical composition and distribution of HC resources were of special interest. The paper also presents the possibilities of borehole interpretation and geological modeling results application for identification of the most favorable zones and evaluation of the resource potential of shale formations.

The article presents the possibilities of applying geological modelling methods in data integration processes for the purpose of the exploration of shale formations and the evaluation of their prospectiveness in terms of the occurrence and quality of unconventional hydrocarbon reservoirs. The analysis involved an onshore part of the Baltic Basin, where Silurian and Ordovician shale formations are the subjects of exploration. The study was carried out in two stages of data integration, i.e.: the integration and interpretation of a wide range of borehole data, and the analysis, integration and processing of coherent well logs and 3D seismic data using the methods of geostatistical 3D modelling. A workflows are presented for modelling the spatial variability of the petrophysical and geochemical parameters determining the prospectiveness of shale formations, i.e. porosity, the organic matter content TOC, as well as the saturation of pore space with reservoir fluids. The validity of the use of 3D seismic data with respect to the prognosis of shale formation parameters has been evaluated. The possibilities of the application of geological modelling results in the identification of zones with the most favourable rock properties, and in the evaluation of the resource potential of shale formations, are also discussed.Key words: 3D geological modelling, shale formations prospectiveness, Silurian and Ordovician shales, Baltic Basin.Modelowanie geologiczne 3D w procesie oceny perspektywiczności formacji łupkowych W artykule przedstawiono możliwości zastosowania metod modelowania geologicznego w procesach integracji danych dla celu rozpoznania formacji łupkowych i oceny ich perspektywiczności pod kątem występowania niekonwencjonalnych złóż węglowodorów. Analizie poddano lądowy fragment basenu bałtyckiego, gdzie przedmiotem eksploracji są formacje łupków syluru i ordowiku. Przeprowadzone prace obejmowały dwa etapy integracji danych, tj.: integrację i interpretację szerokiego zestawu danych otworowych oraz analizę, integrację i przetwarzanie metodami geostatystycznego modelowania 3D spójnych profili otworowych oraz danych sejsmiki 3D. Zaprezentowano tok postępowania w procesie odtwarzania przestrzennej zmienności parametrów petrofizycznych i geochemicznych determinujących perspektywiczność formacji łupkowych, tj. porowatości, zawartości substancji organicznej TOC oraz nasycenia przestrzeni porowej mediami złożowymi. Ocenie poddano celowość aplikacji danych sejsmiki 3D w zagadnieniach prognozy parametrów formacji łupkowych. Omówiono możliwości wykorzystywania wyników modelowania geologicznego w identyfikacji stref o najkorzystniejszych właściwościach skał oraz ocenie potencjału zasobowego formacji łupkowych.Słowa kluczowe: modelowanie geologiczne 3D, perspektywiczność formacji łupkowych, sylurskie i ordowickie formacje łupkowe, basen bałtycki.