Microscopic fracture characterization of gas shale via scratch testing

Akono, Ange-Thérèse; Kabir, Pooyan

doi:10.1016/j.mechrescom.2015.12.003

Cited by 58 publications

(19 citation statements)

References 16 publications

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“…(a) Fine lamination in Barnett shale and granular microstructure of Toarcian shale , (b) a lattice discrete particle model system representing the laminated structure model and a zoomed view of grain interaction, (c) spherical particles placed at the center of shale grains for grain generation, (d) 2D representation of Delaunay tetrahedralization connecting spherical particles, (e) 2D representation of a polyhedral cell generated by a domain tessellation, and (f) a 3D polyhedral cell representing a shale grain. [Colour figure can be viewed at wileyonlinelibrary.com]…”

Section: Discrete Micromechanical Modelingmentioning

confidence: 99%

“…On the basis of the composition and texture of shale described previously, a shale sample at the mesoscopic level (scale 5 in Figure 1) can be represented by a laminated structure model with mul- Figure 2. (a) Fine lamination in Barnett shale [65] and granular microstructure of Toarcian shale [66], (b) a lattice discrete particle model system representing the laminated structure model and a zoomed view of grain interaction, (c) spherical particles placed at the center of shale grains for grain generation, tiple layers of weakness embedded in a stiffer, stronger, and tougher matrix ( Figure 2(b)), which is an analogy for the typical laminated shale as shown in Figure 2(a). The matrix behavior outside the weak layers is dominated by the constituent components of shale, including organic matter, clay, quartz, and other minerals, which also exhibit anisotropic behavior.…”

Section: Discrete Micromechanical Modelingmentioning

confidence: 99%

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A multiscale framework for the simulation of the anisotropic mechanical behavior of shale

Rezakhani

Jin

et al. 2017

Num Anal Meth Geomechanics

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Summary Shale, like many other sedimentary rocks, is typically heterogeneous and anisotropic and is characterized by partial alignment of anisotropic clay minerals and naturally formed bedding planes. In this study, a micromechanical framework based on the lattice discrete particle model is formulated to capture these features. Material anisotropy is introduced through an approximated geometric description of shale internal structure, which includes representation of material property variation with orientation and explicit modeling of parallel lamination. The model is calibrated by carrying out numerical simulations to match various experimental data, including the ones relevant to elastic properties, Brazilian tensile strength, and unconfined compressive strength. Furthermore, parametric study is performed to investigate the relationship between the mesoscale parameters and the macroscopic properties. It is shown that the dependence of the elastic stiffness, strength, and failure mode on loading orientation can be captured successfully. Finally, a homogenization approach based on the asymptotic expansion of field variables is applied to upscale the proposed micromechanical model, and the properties of the homogenized model are analyzed. Copyright © 2017 John Wiley & Sons, Ltd.

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Section: Discrete Micromechanical Modelingmentioning

confidence: 99%

Section: Discrete Micromechanical Modelingmentioning

confidence: 99%

A multiscale framework for the simulation of the anisotropic mechanical behavior of shale

Rezakhani

Jin

et al. 2017

Num Anal Meth Geomechanics

View full text Add to dashboard Cite

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“…The authors aim to address the previous limitation of the estimation in [28], and their results showed much lower values. In measurement using indentation method, results are more of qualitative, and can yield high inaccuracy and subjectivity by virtue of the crack length measurement requiring optical imaging method, which is onerous task for non-translucent rocks like shale [31]. Other method of estimating rock's UCS are the point-load test [32,33].…”

Section: Scratch Test Methods Vs Other Methodsmentioning

confidence: 99%

“…It is a common knowledge that fractures is inherently a multi-scale phenomenon, but a substantial number of studies have limited fractures to the macroscopic sphere. The novel study by [31] was focused on fracture characterization in gas shales using the scratch test method. The authors used shale rocks from 3 systems: Torcian Shale in Paris, Basin, France, and Lower and Upper Woodford shale in Oklahoma, USA.…”

Section: Fracture Toughnessmentioning

confidence: 99%

Evaluation of rock mechanical properties via scratch testing and its impact on energy production: comprehensive review

Kolawole

Ispas

2020

E3S Web Conf.

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The scratch test is a non-destructive method made up of pushing a tool across the surface of a weaker rock at a given penetration depth. The uniaxial rock strength (UCS), fracture toughness (KIC), and other geomechanical parameters influences how fracture nucleates, but fracture sizes and geometry adopted in hydraulic fracture design and modeling are most often overestimated. Although several researchers have attempted to evaluate UCS, KIC and other geomechanical properties in conventional and unconventional formations through scratch testing method, but there remain differing opinions on the fundamental approach and principles to be adopted in estimating those properties. Therefore, the evaluation of geomechanical parameters and their effect on hydrocarbon exploration, energy storage, and hydrocarbon exploitation remain an important issue for energy industry. In this paper, we present a comprehensive review of the methods of approach, applications, and the mechanics of rock scratching. We show the merits of scratch test over other methods of estimating rock mechanical properties. Our review focuses on over 50 previous experimental studies using scratch tests in the past few decades to investigate UCS, KIC and other geomechanical properties, including their impact on rock failure, fracture initiation and propagation. Finally, we highlight the fundamental research questions that are yet to be addressed. We envisage that advancement in our knowledge will improve optimization of hydrocarbon exploitation, energy storage, and field-scale modeling for energy production operations.

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“…At the microscopic length-scale, common toughening mechanisms include crack ligament bridging, as shown in Fig. 2 for Niobrara shale, crack particle bridging [43], distributed microcracking [43], and particle pull-out [8,22]. At the macroscopic scale, the anisotropy of the fracture behavior was attributed to the layered macro-structure and the presence of weak planes, or calcite veins, which promoted crack deflection [23,51].…”

Section: Toughening Mechanisms Of Organic-rich Shale Systemsmentioning

confidence: 99%

Influence of geochemistry on toughening behavior of organic-rich shale

Akono

Kabir

2018

Acta Geotech.

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Our research objective is to understand the influence of geochemistry on the fracture behavior of organic-rich shale at multiple length-scales. Despite an increasing focus on the fracture behavior of organic-rich shale, the relationships between geochemistry and fracture behavior remain unclear and there is a scarcity of experimental data available. To this end, we carry out 59 mesoscale scratch-based fracture tests on 14 specimens extracted from 7 major gas shale plays both in the United States and in France. Post-scratch testing imaging reveal fractures with small crack width of about 400 nm. The fracture toughness is evaluated using the energetic size effect law, which is extended to generic axisymmetric probes. A nonlinear anisotropic and multiscale fracture behavior is observed. In addition, a positive correlation is found between the fracture toughness and the presence of of kerogen, clay and calcite. Moreover, the geochemistry is found to influence the timescale and the regime of propagation of the hydraulic fracture at the macroscopic length-scale. In particular, shale systems rich in TOC, clay and calcite are more likely to exhibit high values of the fluid lag and low hydraulic crack width. Our findings highlight the need for advanced constitutive models for organic-rich shale systems and advanced hydraulic fracturing solutions that can fully integrate the complex fracture response of organic-rich shale materials.

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Microscopic fracture characterization of gas shale via scratch testing

Cited by 58 publications

References 16 publications

A multiscale framework for the simulation of the anisotropic mechanical behavior of shale

A multiscale framework for the simulation of the anisotropic mechanical behavior of shale

Evaluation of rock mechanical properties via scratch testing and its impact on energy production: comprehensive review

Influence of geochemistry on toughening behavior of organic-rich shale

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