Articles | Volume 7, issue 3
Research article
07 Jun 2016
Research article |  | 07 Jun 2016

X-ray CT analyses, models and numerical simulations: a comparison with petrophysical analyses in an experimental CO2 study

Steven Henkel, Dieter Pudlo, Frieder Enzmann, Viktor Reitenbach, Daniel Albrecht, Leonhard Ganzer, and Reinhard Gaupp

Abstract. An essential part of the collaborative research project H2STORE (hydrogen to store), which is funded by the German government, was a comparison of various analytical methods for characterizing 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, Germany), GDF Suez E&P Deutschland GmbH (Lingen, Germany), E.ON Gas Storage GmbH (Essen, Germany) and RAG Rohöl-Aufsuchungs Aktiengesellschaft (Vienna, Austria), were processed by different laboratory techniques; thin sections were prepared, rock fragments were crushed and cubes of 1 cm edge length and plugs 3 to 5 cm in length with a diameter of about 2.5 cm were sawn from macroscopic homogeneous cores. With this prepared sample material, polarized light microscopy and scanning electron microscopy, coupled with image analyses, specific surface area measurements (after Brunauer, Emmet and Teller, 1938; BET), He-porosity and N2-permeability measurements and high-resolution microcomputer tomography (μ-CT), which were used for numerical simulations, were applied. All these methods were practised on most of the same sample material, before and on selected Permian sandstones also 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 area data. The CO2 experiments modified the petrophysical as well as 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 following numerical data simulations was that quite similar data sets and data interpretations were maintained by the different petrophysical standard methods. Moreover, the μ-CT analyses are not only time saving, but also non-destructive. This is an important point if only minor sample material is available and a detailed comparison before and after the experimental tests on micrometre pore scale of specific rock features is envisaged.

Short summary
This study investigates the experimentally induced effects of CO2 storage on underground reservoir sandstones by applying high-resolution computer tomography and standard petrophysical methods. The results of digital rock physic calculations derived from the µ-CT scans are compared with measurements achieved by the standard methods. Both approaches lead to similar results for coarse- and medium-grained sandstones but differ for fine-grained sediments.