Characterization of meso-scale mechanical properties of Longmaxi shale using grid microindentation experiments
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Description
Published version
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4.01 MB
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Checksum (MD5)
569079b9db406859e91e96b34b68c4bf
Author(s)
Du, J
Whittle, AJ
Hu, L
Divoux, T
Meegoda, JN
Date Issued
December 2020
Journal
Journal of Rock Mechanics and Geotechnical Engineering
Publisher
Elsevier BV
Citation
Jianting Du, Andrew J. Whittle, Liming Hu, Thibaut Divoux, Jay N. Meegoda, Characterization of meso-scale mechanical properties of Longmaxi shale using grid microindentation experiments, Journal of Rock Mechanics and Geotechnical Engineering, Volume 13, Issue 3, 2021
Version
Final published version
Abstract
© 2021 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences Mechanical properties, such as the hardness H, Young's modulus E, creep modulus C, and fracture toughness Kc, are essential parameters in the design of hydraulic fracturing systems for prospective shale gas formations. In this study, a practical methodology is presented for obtaining these properties through microindentation experiments combined with quantitative observations of the mineralogical phases using X-ray diffraction (XRD), scanning electron microscopy (SEM) with backscattered electron (BSE) imaging, and energy-dispersive X-ray spectroscopy (EDS) analyses. We apply this method in the case of three types of Longmaxi shales with different mineralogies (i.e. carbonate-, clay-, and quartz-rich, respectively), which allows us to determine the characteristic indentation depth, hc = 8–10 μm, beyond which the mechanical response of the carbonate-rich shale is homogeneous and independent of its complex heterogeneous microstructure. Moreover, exploiting the results of a large number of indentation tests, we demonstrate that the indentation modulus M of the shale increases as a power-law of hardness H, and its creep modulus C increases linearly with H. We also compute the fracture toughness Kc from the indentation data by assuming a perfectly plastic behavior of the sample. Our results are in good agreement with independent measurements of Kc determined by microscratch tests. Finally, further tests on quartz- and clay-rich samples of the Longmaxi shale suggest further variations in the samples’ mechanical properties depending on their burial conditions and the mechanical properties of their dominant mineral phases.
MIT Department
Massachusetts Institute of Technology. Department of Civil and Environmental Engineering
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DOI of Published Version
https://doi.org/10.1016/j.jrmge.2020.09.009
