Geometrical, fractal and hydraulic properties of fractured reservoirs: A mini-review

Wei, Wei; Xia, Yuxuan

doi:10.26804/ager.2017.01.03

Cited by 63 publications

(23 citation statements)

References 61 publications

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“…These properties make them attractive to various applications within the automotive, aerospace, aeronautical and ship building industries [1,2] where they are mainly utilised as cores of composite sandwich structures. In the fields of geoscience and geoengineering, the understanding of underground stress fields around single fractures and fracture networks in porous media are of outmost importance for the investigation of ways to achieve more efficient geothermal energy harvesting, water resource conservation, CO 2 sequestration, and ensuring safe resource exploitation in the oil and gas industry amongst other matters [3,4].…”

Section: Introductionmentioning

confidence: 99%

K-dominance and size effect in mode I fracture of brittle materials with low to medium porosity

Touliatou

Wheel

2018

Engineering Fracture Mechanics

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Linear Elastic Fracture Mechanics usually only considers the singular stresses when describing the conditions under which fracture would occur in a brittle material. However, it is becoming more widely recognised that non-singular stresses can become significant depending on the geometry and configuration of the specimen. This study investigates the impact of non-singular stresses on the stress intensity of low to medium porosity brittle materials. To address this, discrete finite element models of Double Cantilever Beam (DCB) samples were created and the full near-tip stress field in mode I loading was numerically evaluated. A parametric study was conducted, examining the influence of overall specimen size, material porosity and crack tip location relative to the nearest void. Results indicate a prominent size effect on the stress intensity at the crack tip of porous materials, with smaller specimen exhibiting tougher behaviour than their respective larger counterparts. This size effect, which is amplified with increasing porosity, is closely correlated with the variation of non-singular stresses, both parallel and normal to the crack plane. A model to predict the behaviour of porous specimen for different sizes is suggested based on the findings.

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Section: Introductionmentioning

confidence: 99%

K-dominance and size effect in mode I fracture of brittle materials with low to medium porosity

Touliatou

Wheel

2018

Engineering Fracture Mechanics

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“…Further study is necessary to improve the quality of this work. For example, some mathematical analysis or fitting model should be presented, and the "fractal dimension" should also be used to reasonably describe the breaking degree and grain size distribution of the coal [25]. In spite of this, the findings from this study have some engineering implications, and it is found that the appropriate confining pressure is favourable for the improvement in the strength of the grouted crushed coal, which is similar to the other ungrouted rock mass [23,24].…”

Section: Discussionmentioning

confidence: 90%

Mechanical Properties of Grouted Crushed Coal with Different Grain Size Mixtures under Triaxial Compression

Jin

Han

Meng

et al. 2018

Advances in Civil Engineering

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To have a better understanding of the reinforcement effect on the crushed zone after grouting in coal mining extraction work, a self-designed grouting apparatus was used to study the effects of the grain size mixtures (distribution) and the stress state on the mechanical behaviours of grouted crushed coal specimens. From the various grouting tests, triaxial compression tests and scanning electron microscopy (SEM) observations of grouted specimens with different grain size mixtures, it was found that, for the same grain size mixture, the peak (σp) and residual (σr) strengths of the grouted specimens increased with an increase in confining pressure. It was found that the average slope values of the σp-σ3 curves for the grouted specimens with different grain size mixtures were all larger than those of the σr-σ3 curves. It was observed that the peak strain (εp) of the grouted specimens with different grain size mixtures increased overall with increasing confining pressure. For constant confining pressure, the peak and residual strengths both gradually increased approximately linearly as the grain size mixtures varied from small to large, but at higher confining pressures, the influence of the grain size mixture on the peak (or residual) strength increased. These mechanical behaviours of the grouted crushed coal specimens were strongly dependent on the variation in the grain size mixtures and in the confining pressure, which can be explained by the crack evolution process within the grouted specimen under triaxial compression, to a certain extent. Ultimate failure of the grouted specimen occurred just after propagation and coalescence of the cracks through the entire grouted specimen. Moreover, there were three major microscopic diffusion modes for the grouts flowing in most of the crushed coal specimens. Based on these test results, it was found that the reinforcement effect of the grouted specimen related to the splitting grouting mode (occurring in most of the large specimens) seems to be better than that of the penetrating (filling) grouting mode (in most of the small specimens).

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“…Li et al [16] derived the permeability of fracture networks by assuming that each fracture cuts through the model domain from the left inlet boundary to the right outlet boundary when the aperture distribution follows the fractal scaling law. For more compressive summary of recent studies on the relationship between fractal characteristics and permeability, refer to several recent reviews (e.g., [18,19,32]).…”

Section: Introductionmentioning

confidence: 99%

Impact of scaling break and fracture orientation on effective permeability of fractal fracture network

Zhu

2018

SN Appl. Sci.

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Fractures and fracture networks determine the permeability of many natural rocks. In this study, new solutions are developed to calculate the effective permeability of fractal fracture network with non-universal scaling of fracture aperture and trace length. One component of the permeability tensor is derived by assuming that the hydraulic gradient is perpendicular to the trace direction. A new solution is also derived to examine the reduction in the effective permeability of fracture network due to the influence of random fracture orientation. The fracture lengths in the network are assumed to follow the fractal scaling law. The orientation dispersion of factures in the fracture network varies according to the Fisher distribution. The effective permeability is derived by treating the fractal fracture network as a porous medium and using Darcy's law. Results demonstrate that the effective permeability decreases with the scaling exponent before the break when the scaling break occurs early. However, the effective permeability increases with the scaling exponent before the break if the scaling break occurs late. The effective permeability increases with the scaling exponent after the break. The extent of increase varies with the location of the scaling break. If the scaling break occurs early, the increase in the effective permeability is more significant. The effective permeability of fractal fracture network increases with the location of scaling break. The reduction in the effective permeability due to fracture orientation dispersion varies from 2/3 to 0 depending on the degree of orientation dispersion as quantified by the precision parameter.

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Geometrical, fractal and hydraulic properties of fractured reservoirs: A mini-review

Cited by 63 publications

References 61 publications

K-dominance and size effect in mode I fracture of brittle materials with low to medium porosity

K-dominance and size effect in mode I fracture of brittle materials with low to medium porosity

Mechanical Properties of Grouted Crushed Coal with Different Grain Size Mixtures under Triaxial Compression

Impact of scaling break and fracture orientation on effective permeability of fractal fracture network

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