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Badania geofizyczne w rozwiązywaniu problemów cywilizacyjnych istotnych dla Polski

Jarosiński Marek, Krzyścin Janusz, Ustrnul Zbigniew, Kochanek Krzysztof, Janik Tomasz

Przegląd Geologiczny

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2023

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Vol. 71, nr 8

418--429

EN

In view of the challenges faced by geophysical research in the future decades and the observed decline in interest in this field of study in Poland, itis necessary to mobilize the geophysical environment. One of the main causes of the crisis in the popularity of this field of study are changes in the economic paradigm, in which an important determinant and goal of activities is the declared departure from fossil fuels, especially coal and oil. Obviously, this has a direct impact on the prospects of geophysical research, whose main contractor on a global scale is the oil industry. With the depletion of the best available deposits, there is a need to reach for deposits that were increasingly difficult to discover and exploit, which contributed to the progress in geophysical research methods that followed the development of technology and information methods - the basis of modern geophysical analyses. The announced definitive departure from fossil fuels coincided in Poland with the end of the shale-gas boom and the announcement of the program of resigning from coal mining. These announcements aroused the belief that the demand for geophysical research will also expire in the coming years together with the prospects for financing such research. However, this belief is wrong. A significant stream of funds will be directed at the development of geophysical research on a global scale, and the current sponsors of utilitarian geophysical research will occupy new niches on the market, e.g. in the accumulation of energy, storage of greenhouse gases and the search for raw materials, the lack of which is increasingly felt by the most developed economies. Along with the growing awareness of the deepening climate crisis and the destruction of the natural environment engulfing the planet, the need increases to recalculate the environmental costs of economic activity, in which broadly understood geophysical sciences can undoubtedly help. Geophysical analysis of huge datasets requires modern computational methods such as numerical modelling, machine learning and artificial intelligence. The development of these fields will therefore be necessary, but also a difficult challenge for the scientific community in Poland. In this work, we will indicate mainly the prospective areas of the economy and the science, related to the broadly understood energy transformation that requires a significant share of geophysical research. The review of the issues and methodology of current geophysical problems and proposed solutions has been arranged in accordance with the directions of research in the field of earth sciences, subjectively highlighting the tasks that seem to be the most promising and/or scientifically attractive. The text deals with the issues related to climatology, hydrology and hydrogeology, environment, geological hazards, renewable and non-renewable energy sources, waste storage, energy storage, critical raw materials, and the structure and physical condition of the Earth's crust.

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Unconfined compressive strength of Lower Paleozoic shales from the Baltic Basin (northern Poland)

Wojtowicz Michał, Jarosiński Marek, Pachytel Radomir Władysław

Geological Quarterly

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2021

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Vol. 65, No. 2

art. no. 33

EN

Unconfined compressive strength (UCS) is one of the crucial parameters for geomechanical modelling of unconventional reservoirs useful for the design of hydraulic stimulation of hydrocarbon production. In spite of a large amount of UCS data collected from the Lower Silurian and Ordovician shale successions of the Baltic Basin (northern Poland), no comprehensive study on this subject has been published so far. Here, we compile the results of 247 single-stage confined compressive strength tests (CCST) provided by our industrial partner from four exploration boreholes. Based on the integration of these results with geophysical logging data, including dipole sonic logs, we derive empirical equations describing the relationship between UCS and Young’s modulus or sonic wave slowness. Considering the strong anisotropy of elastic properties in shales we have introduced different empirical equations for UCSv (vertical) and UCSh (horizontal), respectively perpendicular and parallel to bedding. The formula for UCSh is determined with less accuracy than for UCSv due to scarce laboratory tests with bed-parallel loading. Based on the empirical formula proposed, we have estimated the VTI-type of anisotropy to be in the range of 12-27%, depending on the lithostratigraphic formation. The results of our UCS estimations are compared with the results of multi-stage CCST from the adjacent borehole. Both confined tests yielded similar results for UCSv, with slightly higher values obtained from the multi-stage tests. In turn, a comparison of our solution with the results of true uniaxial compressive strength tests (UCST) for vertical samples from one of the studied boreholes revealed a significant discrepancy. The mean UCS results for shale formations from UCST are several times lower than those evaluated from the single-stage CCST. The usefulness of the results obtained for borehole breakout analysis is discussed.

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The estimation of CO2 storage potential of a gas-bearing shale succession at the early stage of reservoir characterization : a case study from the Baltic Basin (Poland)

Wójcicki Adam, Jarosiński Marek, Roman Michał Grzegorz

Geological Quarterly

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2021

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Vol. 65, No. 1

art. no. 3

EN

Estimation of the CO2 storage potential of gas-bearing shales in the Lower Paleozoic Baltic Basin is at an early stage of reservoir exploration and production, based on data from one vertical exploration borehole, supplemented with some information from adjacent boreholes. The borehole section examined is 120 m long and comprises three intervals enriched with organic matter separated by organic-poor intervals. In our approach, the storage capacity is represented by: (1) sorption potential of organic matter, (2) open pore space and (3) potential fracture space. The potential for adsorbed CO2 was determined from Langmuir isotherm parameters taken from laboratory measurements and recalculated from CH4 adsorption curves. The pore space capacity was estimated in two ways: by utilizing results of laboratory measurements of dynamic capacity for pores >100 nm and using results of helium porosimetry, the first of these being considered as the most relevant. Due to the low permeability of the shale matrix we have adopted the standard assumption that the CO2 is able to reach effectively only 10% of the theoretical total sorption and pore volume. For hydraulic fracture space, the theoretical maximum opening of vertical fractures in the direction of minimum horizontal stress was considered, decreased by the expected portion of fracturing fluid flowback and by partial fracture closure by burial compaction. The effectiveness of three CO2 storage categories for the individual organic-rich and organic-poor shale units shows an obvious positive correlation of TOC content with the storage efficiency by sorption and within pore space, and a negative correlation with the storage efficiency in hydraulic fractures. It was estimated that sorption, over the maximum storage interval (120 m thick), is responsible for ~76% of total storage capacity, pore space accounts for 13% (for the most relevant porosity model) while the contribution of fractures is 11%. In the minimum storage interval (35 m thick, including the best quality shales) the estimated proportions of sorption, pore space and fractures in the total storage capacity are 84, 10 and 6% respectively. Finally, the result for the best quality storage interval (35 m thick) was compared with the Marcellus Shale of similar thickness (average ~38 m) and with other options of CO2 storage in Poland. The most organic-rich units in the area studied have a CO2 storage capacity efficiency (i.e. storage capacity per volume unit of shale) only slightly less than average for the Marcellus Shale, because sorption capacity – the dominant component – is comparable in both cases. However, the open pore space capacity in the Marcellus Shale appears to be far higher, even if the potential fracture space calculated for the borehole studied is taken into consideration, probably because the free gas content in the Marcellus Shale is far higher than in the Baltic Basin. CO2 storage in depleted shale gas wells is not a competitive solution compared to storage in saline aquifer structures or in larger hydrocarbon fields.

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Tectonics of the Wysoka Kamieńska Graben (NW Poland) and implications for fault sealing potential

Bobek Kinga, Konieczyńska Monika, Jarosiński Marek

Geological Quarterly

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2021

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Vol. 65, No. 3

art. no. 38

EN

Reservoir confinement by faults is important for safe storage of liquid waste or hydrocarbons. Having access to 3D seismic and borehole data, we have interpreted the tectonic setting of the Wysoka Kamieńska Graben (WKG) in the NW part of the Polish Basin and subsequently made an interpretation of the sealing potential of the graben-bounding faults. The formation and development of the graben in the Late Triassic and Early Jurassic was controlled by mechanical decoupling in the salts of the Zechstein Group. The primary tectonic factor triggering the graben origin was dextral strike-slip movement along the regional fault zone in the Paleozoic basement, transtensional accommodation of which in the Zechstein-Mesozoic cover led to development of a horse-tail pattern of grabens. During the Late Cretaceous, the graben underwent minor tectonic inversion. Sealing potential analysis of the graben-bounding faults was performed for the Triassic-Jurassic sequence including juxtaposition seal and fault gouge seal components. Finally, we have focussed our interpretation on the Jurassic sequence where the best reservoirs have been recognized. Our results indicate good to moderate sealing potential of the Hettangian reservoir, poor to moderate sealing of the Pliensbachian reservoir and lack of sealing of the Bajocian reservoir. Hence, the Hettangian reservoir, characterized by large thickness, low clay content and a large regional extent, acts as a potential storage formation, being confined by the graben-bounding faults of the WKG.

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Present-day stress profile in the Baltic Basin sedimentary succession constrained by drilling-induced structures : interpretation uncertainties

Piłacik Alicja, Jarosiński Marek

Geological Quarterly

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2021

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Vol. 65, No. 4

art. no. 51

EN

A far-field stress model based on theory of elasticity and utilizing the Mohr-Coulomb criterion is commonly used in the petroleum industry as a reliable method for present-day stress profiling. We have analysed the present-day stress profile in the Lower Paleozoic shale succession of the Baltic Basin (northern Poland), Based on data from a single borehole. Our analyses take into account the vertical transverse isotropy (VTI) of the mechanical properties. Initial modelling of the stress profile showed - despite general agreement concerning the length and location of the modelled and observed breakouts - systematic differences when the profile of these structures is analysed in detail. Analyses carried out for selected segments of the borehole have shown that the mere presence of breakouts affects the interpretation of the mechanical properties, and thus also the stress profile. We have analysed the size of the necessary correction for tectonic strain, to avoid this effect, as well as uncertainty resulting from the failure criteria adopted. The final model, corrected for stress disturbances by breakouts, reveals the strati fication of stress regime, with the dominance of a normal faulting regime, and low values of differential stresses in the shale formations.

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Modifications of methods for the fracture analysis from borehole data in application to shale formations

Bobek Kinga, Jarosiński Marek

Geological Quarterly

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2021

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Vol. 65, No. 2

art. no. 23

EN

Systematic joints play an important role in effective fluid conductivity and in the mechanical response of shale reservoirs to hydraulic fracturing. Specific features of joints, such as their strata-bound aspect, and their attitude, commonly normal to bedding, make it necessary to modify standard methods of their analysis from borehole data. Our study, based on borehole core and microresistivity image logs, is adjusted to typical exploration procedure, with vertical boreholes penetrating subhorizontal beds. This simple configuration makes it possible to measure the true height of most joints. We have used joint height as the weighting parameter for the construction of orientation diagrams and for computation of fracture intensity profiles. We also propose here a method for evaluation of fracture orientation error on directly oriented core, show how to distinguish joints present in the scanner record but absent from the core, and how to apply this kind of data filtering to core/log correlation. We also propose to extend the analysis of mineralized joints by using the type and degree of vein cracking in order to better characterize their susceptibility to hydraulic stimulation. Application of the modified methods revealed a stratification of joint distribution which, in some cases, may not be observed due to the scarcity of joint data from boreholes.

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Comparison of joint sets orientation in the Lower Paleozoic shales exposed in Scania (SW Sweden) and concealed in N Poland : a multi-methodological approach

Olkowicz Marcin, Bobek Kinga, Jarosiński Marek, Pachytel Radomir

Geological Quarterly

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2021

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Vol. 65, No. 4

s. 258--275

EN

The Lower Paleozoic shales of SW Sweden and Eastern Pomerania (Poland) have a common history related to the depositional and tectonic evolution of the Baltic Basin. The major tectonic events are recorded, among others, as joints, which are either exposed in outcrops in SW Sweden or recognised in deep boreholes located in Pomerania. We present a comparison of the regional joint systems recognized by multiple methods in the studied region. In effect of a statistical compilation of measurements, five joint sets (named JS 1 to JS 5) were identified, traceable between Eastern Pomerania and SW Sweden. Our analysis showed a general consistency of joint set orientations, independent of their distance to the Tornquist tectonic zone passing through the study region. Three of the joint sets, JS 1 striking NNE, JS 2 striking WNW, and JS 3 striking NNW, are found to be the most frequent sets, occurring in most sites. Having more constant orientation, the JS 1 and JS 3 served as indicators of possible rotation of the tectonic block or stress field in the region. JS 1 and JS 2 are interpreted as an effect of late Carboniferous stress relaxation after Variscan collision, while JS 3 and the E–W striking JS 4 might be related to the Early Devonian Caledonian compressive stage.