Characterization of meso-scale mechanical properties of Longmaxi shale using grid microindentation experiments  

作　　者：Jianting Du Andrew J.Whittle Liming Hu Thibaut Divoux Jay N.Meegoda 

机构地区：[1]State Key Laboratory of Hydro-Science and Engineering,Tsinghua University,Beijing,100084,China [2]Department of Civil and Environmental Engineering,Massachusetts Institute of Technology,Cambridge,MA,02139,USA [3]MultiScale Material Science for Energy and Environment,UMI 3466,CNRS-MIT,Cambridge,MA,02139,USA [4]Univ Lyon,Ens de Lyon,Univ Claude Bernard,CNRS,Laboratoire de Physique,Lyon,F-69342,France [5]Department of Civil and Environmental Engineering,New Jersey Institute of Technology,Newark,NJ,07102,USA

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2021年第3期555-567,共13页岩石力学与岩土工程学报（英文版）

基　　金：This research was funded by the National Natural Science Foundation of China(Project Nos.51979144 and 51661165015);State Key Laboratory of Hydroscience and Engineering(Open Research Fund Program 2019-D-03).

摘　　要：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?8e10 mm,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.

关 键 词：Grid microindentation Mineral identification Hardness MODULUS CREEP Fracture toughness 

分 类 号：TU45[建筑科学—岩土工程]