High-resolution 3D fabric and porosity model in a tight gas sandstone reservoir:A new approach to investigate microstructures from mm- to nm-scale combining argon beam cross-sectioning and SEM imaging

The development of new technologies to enhance tight gas reservoir productivity could strongly benefit from a better resolution and imaging of the porosity. Numerous methods are available to characterize sandstone porosity. However, imaging of pore space at scales below 1 μm in tight gas sands remains difficult due to limits in resolution and sample preparation. We explored the use of high resolution SEM in combination with argon ion beam cross sectioning (BIB, Broad Ion Beam) to prepare smooth, and damage-free, true-2D surfaces of tight gas sandstone core samples from the Permian Rotliegend in Germany, to image porosity down to 10 nm. The quality of cross-sections allows measuring porosity at pore scale, and describing the bulk porosity by defining different regions with characteristic pore morphology and pore size distribution. Serial cross sectioning of samples produces a 3D model of the porous network. We present a model of fabric and porosity at 2 different scales: the scale of sand grains and the scale of the clay grains in the intergranular volume.