Samples from four wells in the western Eagle Ford trend of south Texas, USA, were analyzed in a laboratory setting for porosity and permeability using an implementation of the Gas Research Institute (GRI) procedures for fine-grained rock (Guidry et al., 1995). The wells chosen represent a range of thermal maturity levels, from the oil window to the dry gas window. They are also separated by a distance of up to ~120 miles (190 km). Digital rock physics (DRP) models, based on three-dimensional scanning electron microscopy (SEM) volumes, were constructed to determine the porosity-permeability relationship on the micro-scale. Results from the two methods of determining porosity and permeability show similarities, implying that DRP models are generally representative of the larger poro-perm network despite the small DRP sample size. In addition, these SEM volumes were used to quantify volumes of pore space, organic matter, and mineral matrix, and along with 2D SEM images understand the relationships of these elements. Pore type and pore size vary not only with stratigraphic interval, but also with thermal maturity.