Shear-enhanced nonlinear flow in rough-walled rock fractures

Zou, Liangchao; Jing, Lanru; Cvetković, Vladimir

doi:10.1016/j.ijrmms.2017.06.001

Cited by 134 publications

(53 citation statements)

References 41 publications

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“…A fracture comprised of two rough-walled surfaces in the middle of the model (in blue color) was created by using a laser-scanned natural granite rock fracture surface (Koyama et al 2008;Zou et al 2015). Specifically, this fracture model was built by a numerical 'uplift' step that simply extruded up the laser-scanned surface in the vertical height direction (Z -direction) by 0.65 mm and then a 'shear' step that shifted the upper surface along the horizontal length direction (X -direction) with a displacement of 1.0 mm (Zou et al 2016a). Such steps created a numerical 3D fracture model with spatially variable apertures and several contact spots (highlighted in red in Fig.…”

Section: Fracture-matrix Systemmentioning

confidence: 99%

Modeling of Solute Transport in a 3D Rough-Walled Fracture–Matrix System

2017

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Fluid flow and solute transport in a 3D rough-walled fracture-matrix system were simulated by directly solving the Navier-Stokes equations for fracture flow and solving the transport equation for the whole domain of fracture and matrix with considering matrix diffusion. The rough-walled fracture-matrix model was built from laser-scanned surface tomography of a real rock sample, by considering realistic features of surfaces roughness and asperity contacts. The numerical modeling results were compared with both analytical solutions based on simplified fracture surface geometry and numerical results by particle tracking based on the Reynolds equation. The aim is to investigate impacts of surface roughness on solute transport in natural fracture-matrix systems and to quantify the uncertainties in application of simplified models. The results show that fracture surface roughness significantly increases heterogeneity of velocity field in the rough-walled fractures, which consequently cause complex transport behavior, especially the dispersive distributions of solute concentration in the fracture and complex concentration profiles in the matrix. Such complex transport behaviors caused by surface roughness are important sources of uncertainty that needs to be considered for modeling of solute transport processes in fractured rocks. The presented direct numerical simulations of fluid flow and solute transport serve as efficient numerical experiments that provide reliable results for the analysis of effective transmissivity as well as effective dispersion coefficient in rough-walled fracture-matrix systems. Such analysis is helpful in model verifications, uncertainty quantifications and design of laboratorial experiments.

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Section: Fracture-matrix Systemmentioning

confidence: 99%

Modeling of Solute Transport in a 3D Rough-Walled Fracture–Matrix System

2017

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“…Several studies have shown that textures with heterogeneous connectivity structures can strongly impact flow channeling both in porous media (Fiori et al, ; Gotovac et al, ; Vasco et al, ; Zinn & Harvey, ) and in single fractures (Brown, ; Detwiler & Rajaram, ; Nicholl et al, ; Zou et al, , ). A few studies have investigated effects of internal fracture variability in fracture networks, with a range of results indicating minor to notable effects on transport (Cvetkovic & Frampton, ; de Dreuzy et al, ; Frampton et al, ; Makedonska et al, ; Painter, ; Zou et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…This is typically not due to model limitations, but rather because of a lack of comprehensive suitable field information, which reflects the challenges involved in measuring fracture aperture and its variability at multiple scales for in situ field conditions. Several studies have shown that textures with heterogeneous connectivity structures can strongly impact flow channeling both in porous media (Fiori et al, 2010;Gotovac et al, 2009;Vasco et al, 2016;Zinn & Harvey, 2003) and in single fractures (Brown, 1987;Detwiler & Rajaram, 2007;Nicholl et al, 1999;Zou et al, 2015Zou et al, , 2017b. A few studies have investigated effects of internal fracture variability in fracture networks, with a range of results indicating minor to notable effects on transport de Dreuzy et al, 2012;Frampton et al, 2018;Makedonska et al, 2016;Painter, 2006;Zou et al, 2017a).…”

Section: Introductionmentioning

confidence: 99%

Advective Transport in Discrete Fracture Networks With Connected and Disconnected Textures Representing Internal Aperture Variability

Frampton

Hyman

Zou

2019

Water Resources Research

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Flow and transport in three‐dimensional discrete fracture networks with internal variability in aperture and permeability are investigated using a numerical model. The analysis is conducted for three different texture types representing internal variability considering various correlation lengths and for an increase in domain size corresponding to an increase in network complexity. Internal variability in discrete fracture networks generally increases median travel times and delays arrival of bulk mass transport when compared against reference cases without texture, corresponding to smooth fractures. In particular, internal variability textures with weak connectivity increase travel times nonlinearly with domain size increase, further delaying bulk mass arrival. Textures with strong connectivity can however decrease median travel times, accelerating bulk mass arrival, but only for limited ranges of correlation length and domain size. As domain size increases, travel times of textures with strong connectivity converge toward travel times obtained for classical multivariant Gaussian textures. Thus, accounting for internal fracture variability is potentially significant for improving conservative estimates of bulk mass arrival, flow channeling, and advective and reactive transport in large‐scale discrete fracture networks. Further, early mass arrival can arrive significantly earlier for textures with strong connectivity and classical Gaussian textures corresponding to intermediate connectivity but are only slightly affected by textures with weak connectivity. Thus, accounting for internal variability in fractures is also important for accurate estimates of early solute mass arrival. The overall impact on predictive transport modeling will depend on the extent of, or lack of, internal fracture connectivity structure in real‐world fractured rocks.

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“…Recently, shear impacts on flow regimes and nonlinear flow behavior have been investigated by numerical methods and experimental investigations. The numerical simulation studies proposed that shear displacement can enhance the degree of flow nonlinearity and induce nonlinear laminar flow in rough‐walled fractures . However, the shear step is created by artificially moving one half of wall with respect to the other wall, which was not received from physically realistic laboratory test.…”

Section: Introductionmentioning

confidence: 99%

“…The numerical simulation studies proposed that shear displacement can enhance the degree of flow nonlinearity and induce nonlinear laminar flow in rough-walled fractures. 47,48 However, the shear step is created by artificially moving one half of wall with respect to the other wall, which was not received from physically realistic laboratory test. This leads to that the opposite response was observed for the experimental investigations.…”

Section: Introductionmentioning

confidence: 99%

Effect of shearing on hydraulic properties of rough‐walled fractures under different boundary conditions

Wang

Jiang

Luan

et al. 2019

Energy Science & Engineering

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This study experimentally investigated nonlinear flow characteristics of rough‐walled fractures during shear process under different boundary conditions, using the servo‐controlled shear‐flow apparatus. A series of shear‐flow tests were conducted on two types of rough fractures with different shear displacements under various boundary conditions. The effects of shear process, fracture surface roughness, boundary normal stiffness, and initial normal stress on nonlinear flow behaviors are analyzed. The results show that Forchheimer equation provides a good description of the nonlinear relationship between flow rate and pressure gradient in rough‐walled fractures. The linear and nonlinear coefficients decrease by 1‐2 and 2‐3 orders of magnitude during shear, respectively. Both the mechanical aperture and the hydraulic aperture increase with increasing shear displacement. The mechanical aperture is always larger than the hydraulic aperture, and their difference gradually increases with the increment of shear displacement. The contact area ratio exhibits a fast decrease as shear displacement ranges between 1 and 3 mm and then decreases gradually with the decreasing rate generally diminishes. With the increase in shear displacement, the critical Reynolds number shows an increasing trend. The critical Reynolds number is in range 3.22‐35.41 for fracture G1 and 1.23‐12.35 for fracture G3. As the boundary normal stiffness and initial normal stress increase, the critical Reynolds number decreases.

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Shear-enhanced nonlinear flow in rough-walled rock fractures

Cited by 134 publications

References 41 publications

Modeling of Solute Transport in a 3D Rough-Walled Fracture–Matrix System

Modeling of Solute Transport in a 3D Rough-Walled Fracture–Matrix System

Advective Transport in Discrete Fracture Networks With Connected and Disconnected Textures Representing Internal Aperture Variability

Effect of shearing on hydraulic properties of rough‐walled fractures under different boundary conditions

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