Heterogeneities in the elastic properties of microporous carbonate rocks at the microscale from nanoindentation tests

Abstract

In this study, we used nanoindentation technique to map Young’s modulus of microporous limestones at the microscale (map of 300*300 µm2, with a step measurement of 10 µm). Results show a broad distribution of moduli, from very low values to values consistent with calcite mineral. Because the length scale of heterogeneities of the probed areas was larger than the indent size, the samples can be seen as composites of different phases and upscaling rock physics models such as self-consistent approximation can be used to get the effective elastic properties. Scanning Electron Microscopy (SEM) imaging of the same probed areas allowed to correlate micrite microstructure to elastic properties: the more microporous micrites displayed Young’s moduli as low as 9 GPa and the tighter ones as high as 64 GPa.