Variability of the Rotliegend sandstones in the Polish part of the Southern Permian Basin - permeability and porosity relationships

The Flow Zone Index, FZI, applied to order relations between the effective porosity and permeability of the Rotliegend sandstones in the Polish part of the Southern Permian Basin turns out to be a useful and effective factor to evaluate ability of media flow in a rock formation. A dataset of over 2000 samples from 78 wells was analysed. Based only on porosity and permeability, FZI includes all non-parameterized features of rocks as tortuosity and diameters of porous channels, volume of trapped parts of capillary roads, specific surface of pore space, and others. When FZI increases, the ability of fluid to move through the porous space increases. In most cases, the Rotliegend sandstones reveal FZI in the range of 0.5-2.0. The highest FZI, ca. 100, is related to fractured part of the studied formation. The combination of FZI and facies information from several wells in the study area (over 1200 samples) showed a good correlation. On the basis of FZI we can divide a set of samples of the Rotliegend sandstone into groups of defined fluid flow abilities and relate them to facies. Also, we show the way of estimation of the reliable values of permeability in full geological log of a borehole on the basis of FZI, and the total porosity determined from well logging interpretation.