Discrete Element Modeling of Micro-scratch Tests: Investigation of Mechanisms of CO2 Alteration in Reservoir Rocks

Sun, Zhuang; Espinoza, D. Nicolas; Balhoff, Matthew T.; Dewers, Thomas

doi:10.1007/s00603-017-1306-z

Cited by 33 publications

(8 citation statements)

References 50 publications

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“…A similar ductile behaviour of highly porous sandstone has been reported by Klein et al (2001) in Bentheim sandstone as "quasi-ductile failure". Similar ductile behaviour was reported by Sun et al (2017) and they explained that it is a result of reduction in the cement size due to CO 2 -brine-rock interaction. Furthermore, Scott and Nielsen (1991) explained that brittle-ductile transition depends on the initial porosity of the sandstone but that increasing the confining pressure has the effect of shifting the brittle-ductile boundary to lower porosities and vice-versa.…”

Section: Triaxial Compression and Micromechanical Propertiessupporting

confidence: 85%

Effect of CO2 Phase on Pore Geometry of Saline Reservoir Rock

et al. 2022

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The phase of CO2 present in a saline reservoir influences the change of the pore geometry properties of reservoir rocks and consequently the transport and storage integrity of the reservoir. In this study, digital rock physics was used to evaluate pore geometry properties of rocks saturated with the different phaseCO2-brine under reservoir conditions. The changes in the pore geometry properties due to the different phaseCO2-brine-rock interaction were quantified. In addition to compression, CO2-brine-rock interaction caused a further reduction in porosity by precipitation. Compared to the dry sample, the porosity of the gaseous CO2-br sample was reduced the most, and was lower by 15% after saturation and compression. There was reduction in the pre-compression porosity after compression for all the samples, however, the reduction was highest in the gaseous CO2-br-saturated sample (13%). The flatness of pore surfaces was reduced, and pores became less rounded after compression, especially in supercritical CO2-br-saturated rock. The results from this research provide a valuable input to guide a robust simulation of CO2 storage in reservoir rocks where different phases of CO2 could be present.

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Section: Triaxial Compression and Micromechanical Propertiessupporting

confidence: 85%

Effect of CO2 Phase on Pore Geometry of Saline Reservoir Rock

et al. 2022

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“…The macroscopic mechanical behavior emerges from the interplay of mostly rigid particles through their contacts at the microscale [32]. Detailed model formulation of the DEM can be found in our previous work [61,62]. The CFD is a direct numerical simulation approach to describe the fluid flow and involves the discretization and solution of the Navier-Stokes (N-S) equation in space and time using various numerical methods, e.g.…”

Section: Numerical Approachmentioning

confidence: 99%

Fluid-driven fractures in granular media: Insights from numerical investigations

Sun

Espinoza

et al. 2020

Phys. Rev. E

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We investigate the mechanisms of opening-mode fracture initiation in granular media. The study 11 is based on simulation of grain-scale fluid-grain interactions through a coupled numerical approach in which the discrete element model (DEM) is used to solve for the mechanics of a solid granular medium and computational fluid dynamics (CFD) is used to model fluid flow and drag forces. We present benchmark problems with analytical solutions and validate this numerical model against experiments of viscous-drag driven cavity in the literature. Additional simulation results show fracture initiation mechanisms in a random granular packing subjected to constant boundary stresses and to fluid injection with a localized source. The dimensionless variable F s /F sk (ratio of seepage force F s and skeletal force F sk ) incorporates the impacts of 19 physical properties and injection parameters including fluid viscosity, injection velocity, grain 20 size and effective stresses, and has been used as a criterion separating regimes of fluid invasion 21 and drag-driven fracture opening. Our simulation results show that F s /F sk in combination with τ 1 (ratio of diffusion time from hydromechanical coupling and injection time) serve as a prediction of fracture opening within granular packing. We suggest a simple criterion (F s /F sk > 1 or τ 1 > 0.17) that is valid for various types of granular media and injection conditions to determine if fracture opening will occur. Among other applications, this study is useful to predict the initiation and propagation of fractures in natural sediments.

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“…Seven years ago, we introduced the method of fracture assessment via scratch testing. The theory and Since then, the method has been widely used to characterize reservoir rocks [75], tribological coatings [58,27], steel tools [70], coal [54], and rocks [32], and other appications. The scratch test consists of drawing a Rockwell C diamond stylus across the flat surface of the specimen under a progressively increasing vertical load and a constant scratch speed of 6 mm/min.…”

Section: Scratch Testingmentioning

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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Discrete Element Modeling of Micro-scratch Tests: Investigation of Mechanisms of CO2 Alteration in Reservoir Rocks

Cited by 33 publications

References 50 publications

Effect of CO2 Phase on Pore Geometry of Saline Reservoir Rock

Effect of CO2 Phase on Pore Geometry of Saline Reservoir Rock

Fluid-driven fractures in granular media: Insights from numerical investigations

Influence of geochemistry on toughening behavior of organic-rich shale

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