Direct measurement of contact area and stress dependence of anisotropic flow through rock fracture with heterogeneous aperture distribution

Nemoto, Katsumi; Watanabe, Noriaki; Hirano, Nobuo; Tsuchiya, Noriyoshi

doi:10.1016/j.epsl.2009.02.005

Cited by 137 publications

(81 citation statements)

References 27 publications

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“…Thus, various analytical equations, experimental tests and numerical methods have been proposed to quantify the aperture distribution and flow behavior in the fracture under normal and shear stresses. [8][9][10][11] Single fracture has been approximately modeled by using two smooth parallel plates that are separated by a constant distance, with the fluid flowing through it that follows the cubic law. 12,13 However, in the nature, the surfaces of most rock fractures are rough, which results in nonuniformly distributed aperture fields in fractures.…”

Section: Introductionmentioning

confidence: 99%

Size Effect on the Permeability and Shear Induced Flow Anisotropy of Fractal Rock Fractures

et al. 2018

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The effect of model size on fluid flow through fractal rough fractures under shearing is investigated using a numerical simulation method. The shear behavior of rough fractures with selfaffine properties was described using the analytical model, and the aperture fields with sizes ¶ Corresponding author. This is an Open Access article published by World Scientific Publishing Company. It is distributed under the terms of the Creative Commons Attribution 4.0 (CC-BY) License. Further distribution of this work is permitted, provided the original work is properly cited. varying from 25 to 200 mm were extracted under shear displacements up to 20 mm. Fluid flow through fractures in the directions both parallel and perpendicular to the shear directions was simulated by solving the Reynolds equation using a finite element code. The results show that fluid flow tends to converge into a few main flow channels as shear displacement increases, while the shapes of flow channels change significantly as the fracture size increases. As the model size increases, the permeability in the directions both parallel and perpendicular to the shear direction changes significantly first and then tends to move to a stable state. The size effects on the permeability in the direction parallel to the shear direction are more obvious than that in the direction perpendicular to the shear direction, due to the formation of contact ridges and connected channels perpendicular to the shear direction. The variances of the ratio between permeability in both directions become smaller as the model size increases and then this ratio tends to maintain constant after a certain size, with the value mainly ranging from 1.0 to 3.0. 1840001-1

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Section: Introductionmentioning

confidence: 99%

Size Effect on the Permeability and Shear Induced Flow Anisotropy of Fractal Rock Fractures

et al. 2018

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“…By contrast, quantification of fracture flow was performed by Indraratna et al (2015), who performed CFD simulations based on initial laser-scanning measurements, where the flow model is coupled with a deformation criteria simulating fracture closing. Similar, but more simplified, deformation procedures were performed for statistically derived aperture distributions (Pyrak-Nolte and Morris, 2000), profilometer measurements (Kim et al, 2003), laser-scan data (Nemoto et al, 2009;Watanabe et al, 2008Watanabe et al, , 2009) and a conceptual 2-D model (Liu et al, 2010). Furthermore, Dicman et al (2004) described changes in aperture distribution by combining laboratory data and stochastic approaches.…”

Section: Introductionmentioning

confidence: 99%

Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

et al. 2016

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Abstract. Various geoscientific applications require a fast prediction of fracture permeability for an optimal workflow. Hence, the objective of the current study is to introduce and validate a practical method to characterize and approximate single flow in fractures under different stress conditions by using a core-flooding apparatus, in situ X-ray computed tomography (CT) scans and a finite-volume method solving the Navier-Stokes-Brinkman equations. The permeability of the fractured sandstone sample was measured stepwise during a loading-unloading cycle (0.7 to 22.1 MPa and back) to validate the numerical results. Simultaneously, the pressurized core sample was imaged with a medical X-ray CT scanner with a voxel dimension of 0.5 × 0.5 × 1.0 mm 3 . Fracture geometries were obtained by CT images based on a modification of the simplified missing attenuation (MSMA) approach. Simulation results revealed both qualitative plausibility and a quantitative approximation of the experimentally derived permeabilities. The qualitative results indicate flow channeling along several preferential flow paths with less pronounced tortuosity. Significant changes in permeability can be assigned to temporal and permanent changes within the fracture due to applied stresses. The deviations of the quantitative results appear to be mainly caused by both local underestimation of hydraulic properties due to compositional matrix heterogeneities and the low CT resolution affecting the accurate capturing of sub-grid-scale features. Both affect the proper reproduction of the actual connectivity and therefore also the depiction of the expected permeability hysteresis. Furthermore, the threshold value CT mat (1862.6 HU) depicting the matrix material represents the most sensitive input parameter of the simulations. Small variations of CT mat can cause enormous changes in simulated permeability by up to a factor of 2.6 ± 0.1 and, thus, have to be defined with caution. Nevertheless, comparison with further CT-based flow simulations indicates that the proposed method represents a valuable method to approximate actual permeabilities, particularly for smooth fractures (< 35 µm). However, further systematic investigations concerning the applicability of the method are essential for future studies. Thus, some recommendations are compiled by also including suggestions of comparable studies.

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“…Methods based on inserting or injecting some materials such as pressure-sensitive film (Nemoto et al 2009), special metal (Pyrak-Nolte et al 1987), or epoxy resin (Hakami and Larsson 1996) into the joint interface. The main problem in using pressure-sensitive film methods is the thickness of the material.…”

Section: Description Of the New Methods For Joint Surface Characterizamentioning

confidence: 99%

Geometric Effect of Asperities on Shear Mechanism of Rock Joints

et al. 2015

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Three-dimensional tracking of changes of asperities is one of the most important ways to illustrate shear mechanism of rock joints during testing. In this paper, the changes of the role of asperities during different stages of shearing are described by using a new methodology for the characterization of the asperities. The basis of the proposed method is the examination of the three-dimensional roughness of joint surfaces scanned before and after shear testing. By defining a concept named 'tiny window', the geometric model of the joint surfaces is reconstructed. Tiny windows are expressed as a function of the x and y coordinates, the height (z coordinate), and the angle of a small area of the surface. Constant normal load (CNL) direct shear tests were conducted on replica joints and, by using the proposed method, the distribution and size of contact and damaged areas were identified. Image analysis of the surfaces was used to verify the results of the proposed method. The results indicated that the proposed method is suitable for determining the size and distribution of the contact and damaged areas at any shearing stage. The geometric properties of the tiny windows in the pre-peak, peak, post-peak softening, and residual shearing stages were investigated based on their angle and height. It was found that tiny windows that face the shear direction, especially the steepest ones, have a primary role in shearing. However, due to degradation of asperities at higher normal stresses and shear displacements, some of the tiny windows that do not initially face the shear direction also come in contact. It was also observed that tiny windows with different heights participate in the shearing process, not just the highest ones. Total contact area of the joint surfaces was considered as summation of just-in-contact areas and damaged areas. The results of the proposed method indicated that considering differences between just-in-contact areas and damaged areas provide useful insights into understanding the shear mechanism of rock joints.

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Direct measurement of contact area and stress dependence of anisotropic flow through rock fracture with heterogeneous aperture distribution

Cited by 137 publications

References 27 publications

Size Effect on the Permeability and Shear Induced Flow Anisotropy of Fractal Rock Fractures

Size Effect on the Permeability and Shear Induced Flow Anisotropy of Fractal Rock Fractures

Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

Geometric Effect of Asperities on Shear Mechanism of Rock Joints

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