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Open AccessArticle

Quantifying Rock Weakening Due to Decreasing Calcite Mineral Content by Numerical Simulations

by Maria Wetzel 1,2,*, Thomas Kempka 1,2 and Michael Kühn 1,2
1
Fluid Systems Modelling, GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany
2
Institute of Earth and Environmental Science, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany
*
Author to whom correspondence should be addressed.
Materials 2018, 11(4), 542; https://doi.org/10.3390/ma11040542
Received: 16 February 2018 / Revised: 21 March 2018 / Accepted: 29 March 2018 / Published: 1 April 2018
The quantification of changes in geomechanical properties due to chemical reactions is of paramount importance for geological subsurface utilisation, since mineral dissolution generally reduces rock stiffness. In the present study, the effective elastic moduli of two digital rock samples, the Fontainebleau and Bentheim sandstones, are numerically determined based on micro-CT images. Reduction in rock stiffness due to the dissolution of 10% calcite cement by volume out of the pore network is quantified for three synthetic spatial calcite distributions (coating, partial filling and random) using representative sub-cubes derived from the digital rock samples. Due to the reduced calcite content, bulk and shear moduli decrease by 34% and 38% in maximum, respectively. Total porosity is clearly the dominant parameter, while spatial calcite distribution has a minor impact, except for a randomly chosen cement distribution within the pore network. Moreover, applying an initial stiffness reduced by 47% for the calcite cement results only in a slightly weaker mechanical behaviour. Using the quantitative approach introduced here substantially improves the accuracy of predictions in elastic rock properties compared to general analytical methods, and further enables quantification of uncertainties related to spatial variations in porosity and mineral distribution. View Full-Text
Keywords: digital rock physics; micro-CT; elastic properties; numerical simulation; chemical-mechanical interaction; Code_Aster; composite properties digital rock physics; micro-CT; elastic properties; numerical simulation; chemical-mechanical interaction; Code_Aster; composite properties
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Wetzel, M.; Kempka, T.; Kühn, M. Quantifying Rock Weakening Due to Decreasing Calcite Mineral Content by Numerical Simulations. Materials 2018, 11, 542.

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