The main goal of the research was to employ the unique data delivered by various methods to improve the determination of rock reservoir properties. Results of Xray computed tomography (XRCMT), one of the newest techniques providing high-resolution images of rocks, were used to show that very precise information from this tool is complementary to results from other methods. Standard laboratory measurements (helium pycnometer, mercury injection porosimetry, permeameter) and sophisticated experiments (X-ray computed tomography and nuclear magnetic resonance spectroscopy) were performed to obtain and compare results. Four types of specimens: typical Miocene sandstone-mudstone-claystone rock samples, artificial corundum specimens, shale gas plugs, and limestone sample were investigated to obtain the porosity, permeability, density, and other parameters used in rock descriptions. Mutual relationships between selected groups of rock material properties were presented to provide an integral picture of rock characteristics. The XRCMT results were in general not influenced by lithology, but there were observed Oil and Gas Institute -National Research Institute, Krakow, Poland shaliness effects on the shape of pores, cross sections, and the tortuosity of porous channels. An analysis of the average porosity and the standard deviation of each XRCMT plot provided information about differences in the heterogeneity of a formation. Thus, the XRCMT method was recommended in pore space parameter determination for microfracture fluid propagation monitoring. There was also observed equivalence between part of the NMR signal from clay-bound water and the XRCMT volume subgroups in porosity/permeability-structural classes I and II. So, the use of the two-subsample approach in the XRCMT interpretation was promoted.

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An example of interpretation of the Silurian and Ordovician shale formations in the Baltic Basin in Poland regarding determination of potential sweet spots is presented. Short geological information shows the position of shale gas play. Description of the data-laboratory measurement outcomes (petrophysical and geochemical) and well logging-presents results available for analyses. Detailed elemental analyses and various statistical classifications show the differentiation between sweet spots and adjacent formations. Elastic property modelling based on the known theoretical models and results of comprehensive interpretation of well logs is a good tool to complete information, especially in old wells. Acoustic emission investigations show additional characteristic features of shale gas rock and reveal that acoustic emission and volumetric strain of a shale sample induced by the sorption processes are lower for shale than for coals.

This paper presents an application of rock physics templates constructed with the use of the granular effective medium theory and the shale model to estimate the elastic properties of the Silurian and Ordovician shale formations from the Baltic Basic, Poland. The author uses available logging data from three nearby wells and their petrophysical interpretation to distinguish various lithologies and to determine average matrix mineral composition of each lithology group, essential in further rock physics modelling. Anisotropy estimation and investigation of the relation between various petrophysical parameters precede the rock physics modelling. The logging data cross-plotted in Vp/Vs ratio-acoustic impedance domain reveals distinct compaction trend for shales, which is not followed by shales with increased organic matter and calcareous deposits. These two lithology groups present own trends, which are related to increasing kerogen and carbonate minerals contents, respectively. The trends are the subject of rock physics modelling. Granular effective medium rock physics templates are constructed for each lithology group. The rock physics analyses reveal that the elastic properties of strongly compacted shales, including shales with organic matter, might be successfully described by the lower modified Hashin-Shtrikman bound, which is useful in compaction trend modelling. Marly deposits can be modelled in a similar way to shales. The upper modified Hashin-Shtrikman bound provides a better template for carbonates as it models the cementation process. The shale model provides independent rock physics template for shales. Comparison of these two approaches shows that the granular effective medium method better describes the elastic properties of the analysed formations. The paper includes also the proposition of the final rock physics template constructed for the Silurian and the Ordovician formation from the Baltic Basin that can contribute to a better understanding of the elastic properties of the lower Paleozoic shale plays in Poland.

Several data sets from the Silurian and Ordovician formations from three wells on the shore of Baltic Basin in Northern Poland prepared on the basis of well logging data and results of their comprehensive interpretation were used in factor analysis. The goal of statistical analysis was structure recognition of data and proper selection of parameters to limit the number of variables in study. The top priority of research was recognition of specific features of claystone/mudstone formations predisposing them to be potential shale gas deposits. The identified data scheme based on data from one well, was then applied to: 1) well 2 and well 3 separately, 2) combined data from three wells, 3) depth intervals treated as sweet spots, i.e., formations of high hydrocarbon potential. Numbers of samples from well logging were proportional to number of laboratory data from individual formations. The extended data set comprising all available log samples in explored formations was also prepared. Outcomes from standard (Triple Combo-natural gamma log, resistivity log, neutron log and bulk density log and Quad Combo-with addition of sonic log and spectral gamma log) and sophisticated (GEM™-Elemental Analysis Tool, Wave Sonic and Nuclear Magnetic Resonance-NMR) logs were the basis for data sets. Finally, laboratory data set of huge amount of variables from elemental, mineralogical, geochemical and petrophysical laboratory experiments was built and verified in FA to select the most informative components. Conclusions on the data set size, number of factors and type of variables were drawn.