Data from x-ray diffraction analyses (XRD) was combined with conventional, broad ion beam (BIB), and focused ion beam (FIB) scanning electron microscopy (SEM) to evaluate Upper Visean “Rudov Beds” (V-23), one of the main source rocks in the Ukrainian Dniepr-Donets Basin (DDB; e.g. Sachsenhofer et al., 2010; Misch et al., 2015), as a target for unconventional production. XRD data and SEM imaging suggests strongly variable mineralogy and, therefore, mechanical properties of Rudov Beds in both lateral and vertical extent. OM-hosted nanopores, important for hydrocarbon storage and release, are restricted to secondary (pyro)bitumen. Their frequency strongly increases at a vitrinite reflectance >2.0 %Rr. Furthermore, nanoscale authigenic clay and calcite particles within pyrobitumen start to grow at gas window maturity. Sub-micrometer- to nanopores have been detected in bituminous pore fillings already at 0.65 to 0.9 %Rr, in samples that are classified as oil-prone from Py-GC and biomarker studies. In contrast, primary and secondary OM within samples from marginal positions dominated by terrestrial macerals did not host nanopores up to 1.35 %Rr. Therefore, minor generation of nanopores within bitumen, due to hydrocarbon generation, might already start at oil window maturity, but the main stage of development occurs between 1.35 %Rr and 2.0 %Rr.