Quantifying rock weakening due to decreasing calcite mineral content by numerical simulations

  • 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 aThe 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.show moreshow less

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Metadaten
Author details:Maria WetzelORCiD, Thomas KempkaORCiD, Michael KühnORCiD
URN:urn:nbn:de:kobv:517-opus4-473089
DOI:https://doi.org/10.25932/publishup-47308
ISSN:1866-8372
Parent title (German):Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
Publication series (Volume number):Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe (1092)
Document type:Postprint
Language:English
Date of first publication:2021/01/13
Year of completion:2018
Publishing institution:Universität Potsdam
Release date:2021/01/13
Tag:Code_Aster; chemical-mechanical interaction; composite properties; digital rock physics; elastic properties; micro-CT; numerical simulation
Issue:1092
Page number:21
Source:Materials 11 (2018) 4, Art. 542 DOI: 10.3390/ma11040542
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Geowissenschaften
DDC classification:6 Technik, Medizin, angewandte Wissenschaften / 60 Technik / 600 Technik, Technologie
Peer review:Referiert
Grantor:Multidisciplinary Digital Publishing Institute (MDPI)
Publishing method:Open Access / Green Open-Access
License (German):License LogoCreative Commons - Namensnennung, 4.0 International