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CT Imaging of Rock Salt: 3-D Multi-Scale Analyses of the Structural Inventory


Non-destructive CT imaging is an established technique in geosciences (see Mees et al. 2003 and references therein). However, CT studies of rock salt are rare (e.g. Zulauf et al. 2009, 2012, Burliga & Czechowski 2010, Mertineit et al. 2012). We present scientific approaches and possibilities of CT investigations on rock salt using a Phoenix nanotom s (GE Sensing and Inspection Technologies) at the Goethe University of Frankfurt am Main. This μ-CT has a maximum resolution of less than 1 μm per voxel and allows high resolution scans amplifying and improving CT studies acquired by clinic computer tomographs. CT analyses are capable for visualisation and quantification of any detectable portion of a rock volume depending on density contrast and the designated scale. In the case of rock salt, pore space, fractures or mineral assemblages (e. g. anhydrite or celestine) can be analysed and quantified. Moreover, three-dimensional visualisations expose spatial distribution anisotropies of pore space to give important additional information to laboratory measurements or macro- and microscopic observations regarding porosity, permeability and reservoir properties. An elevated porosity (< 1.3 Vol.-%) can be observed in hydrocarbon-bearing rock salt samples from salt diapirs, implying that hydrocarbons are responsible for hampered closure of pore space during the halokinetic uprise. Generally, CT imaging supports the overall characterisation and interpretation of structural inventories of rock salt and helps to uncover the distribution of mineral phases or fluids and the deformation history of the salt rocks on multiple requested scales.