Petrophysical characteristics of Silurian and Ordovician shale gas formations in the Baltic Basin (Northern Poland)

Abstract

This paper presents findings from the study into the relationships between the laboratory- and well log-derived data (including the comprehensive well-log interpretation data) on petrophysical properties of the Silurian and Ordovician shale gas formations in the Baltic Basin (North Poland). Approximately 70 samples of mudstone were examined in laboratory experiments to determine total and effective porosity; bulk, grain, and rock density; total organic carbon; physical permeability; total pore area, pore distribution; and mineral components. Some rock samples were further investigated using mercury injection porosimetry, helium porosimetry, dual liquid porosimetry, NMR, N2 adsorption/desorption, rock-eval pyrolysis, and XRD to obtain the targeted petrophysical information from heterogeneous claystone/mudstone and their organic matter. Natural radioactivity, bulk density, total porosity, volume of kerogen, and other parameters were determined from the continuous curves plotted from the earlier depth matched well logging data, which were used to account for differences between vertical resolution of well logs and the point data obtained from the laboratory. The goal of this study was to provide a comprehensive characterization of the Silurian and Ordovician shale gas formations in Northern Poland to support the thesis about their heterogeneity.