X-Ray CT analyses, models and numerical simulations – a comparison with common analytical methods of an experimental CO<sub>2</sub> study

Abstract. An essential part of the collaborative research project H2STORE ("hydrogen to store"), which is founded by the German government, was a comparison of various analytical methods to characterize reservoir sandstones from different stratigraphic units. In this context Permian, Triassic and Tertiary reservoir sandstones were analysed. Rock core materials, provided by RWE Gasspeicher GmbH (Dortmund), GFD Suez E&P Deutschland GmbH (Lingen), E.ON Gas Storage GmbH (Essen) and RAG Rohöl-Aufsuchungs Aktiengesellschaft (Wien), was processed by different laboratory techniques; thin sections were prepared, rock fragments were crushed, cubes of 1 cm edge length and plugs of 5 cm in length were sawn from macroscopic homogenous cores. With this prepared sample material, polarized light microscopy and scanning electron microscopy – coupled with image analyses, specific surface area measurements (BET), He-porosity and N2-permeability measurements and high resolution micro-computer-tomography (µ-CT), which were used for numerical simulations were conducted. All these methods were applied to most of the same sample material, before and after static CO2 experiments under reservoir conditions. A major concern in comparing the results of these methods is an appraisal of the reliability of the given porosity, permeability and mineral specific reactive (inner) surface areas data. The CO2 experiments are modifying the petrophysical as well the mineralogical/geochemical rock properties. These changes are detectable by all applied analytical methods. Nevertheless, a major outcome of the high resolution µ-CT analyses and proceeded numerical data simulations results in quite similar data sets and data interpretations maintained by the different standard methods; even regarding only CT-single scan of the rock samples. Moreover, this technique is not only time saving, but also none destructive. This is an important point, if only minor sample material is available and a detailed comparison before and after the experimental tests on micro meter, pore scale of specific rock features is envisaged.