Mapping fracture aperture as a function of normal stress using a combination of casting, image analysis and modeling techniques

Gentier, Sylvie; Hopkins, Deborah

doi:10.1016/s1365-1609(97)00234-7

Cited by 14 publications

(4 citation statements)

References 2 publications

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“…Noiriel, 2005) or resin injection into the fracture (e.g. Gentier and Hopkins, 1997; Hakami and Larsson, 1996). In the study by Hakami and Larsson, 1996, the sample was then sliced perpendicularly to the fracture, and the aperture was measured on each slide using images obtained from an optical microscope.…”

Section: Introductionmentioning

confidence: 99%

Fracture aperture reconstruction and determination of hydrological properties: a case study at Draix (French Alps)

Neuville

Toussaint

Schmittbuhl

2011

Hydrological Processes

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International audienceWe propose two techniques for fracture aperture reconstruction. The first one is a correlation technique that estimates the normal aperture or the tangential shift across a discontinuity whose sides present geometrical similarities. The only required material is a pair of appropriately controlled images of each side. Here, the images are maps of the corresponding side topography, obtained from laser profilometry. Assuming a purely normal opening, it is possible, from two corresponding sides of a given discontinuity in a core log, to infer the precise geometry of the in situ aperture. The second technique allows to retrieve the three-dimensional geometry of a sealed discontinuity from non-independent topography measurements of both sides. Both techniques are applied to discontinuities extracted from a core drilled down to 20 m in a fractured marl formation at Draix (French Alps). The probability density functions of the aperture of the sealed and open discontinuities are shown to be Gaussian. At the sample scale, the sealed fracture aperture is self-affine, while the open one shows a cross-over from a self-affine regime at very small scales to an uncorrelated regime at largest scales. After extrapolating those scaling laws at the scale of the whole formation, we discuss when the aperture roughness affects the hydraulic properties of the Draix fractured bedrock. The overall estimated permeability is significant (10−9 − 10−8 m2), consistently with some previous indirect inferences

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Section: Introductionmentioning

confidence: 99%

Fracture aperture reconstruction and determination of hydrological properties: a case study at Draix (French Alps)

Neuville

Toussaint

Schmittbuhl

2011

Hydrological Processes

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“…The present paper does not address this scenario but rather focuses on those rock masses whose permeability is strongly controlled by the current stress state. Moreover, fractures having significant shear displacement will have locally anisotropic transmissivity, with higher transmissivity in the direction perpendicular to the shear direction than parallel to it, as has been shown theoretically (Mallikamas & Rajaram, 2005) and experimentally (Auradou et al, 2005;Gentier & Hopkins, 1997;Matsuki et al, 2006;Nemoto et al, 2009;Yeo et al, 1998). This occurs primarily because aperture correlation is less persistent in the sliding direction as compared to the normal direction (Mallikamas & Rajaram, 2005;Nemoto et al, 2009).…”

Section: Introductionmentioning

confidence: 85%

“…The directional nature of this displacement results in an anisotropic void space (Figure ), where flow channels tend to show more pronounced percolation perpendicular (⊥) to the direction of relative displacement than parallel (∥) to it. The ensuing anisotropy of fracture transmissivity has been measured as 1–1,000 (Gentier & Hopkins, ; Matsuki et al, ; Nemoto et al, ; Yeo et al, ) for laboratory‐scale fractures. These experiments are set up to preserve the original surface roughness and to not allow for abrasion‐related damage during the shear displacement.…”

Section: Methodsmentioning

confidence: 99%

Relationship Between the Orientation of Maximum Permeability and Intermediate Principal Stress in Fractured Rocks

Lang

Paluszny

Nejati

et al. 2018

Water Resources Research

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Flow and transport properties of fractured rock masses are a function of geometrical structures across many scales. These structures result from physical processes and states and are highly anisotropic in nature. Fracture surfaces often tend to be shifted with respect to each other, which is generally a result of stress‐induced displacements. This shift controls the fracture's transmissivity through the pore space that forms from the created mismatch between the surfaces. This transmissivity is anisotropic and greater in the direction perpendicular to the displacement. A contact mechanics‐based, first‐principle numerical approach is developed to investigate the effects that this shear‐induced transmissivity anisotropy has on the overall permeability of a fractured rock mass. Deformation of the rock and contact between fracture surfaces is computed in three dimensions at two scales. At the rock mass scale, fractures are treated as planar discontinuities along which displacements and tractions are resolved. Contact between the individual rough fracture surfaces is solved for each fracture at the small scale to find the stiffness and transmissivity that result from shear‐induced dilation and elastic compression. Results show that, given isotropic fracture networks, the direction of maximum permeability of a fractured rock mass tends to be aligned with the direction of the intermediate principal stress. This reflects the fact that fractures have the most pronounced slip in the plane of the maximum and minimum principal stresses, and for individual fractures transmissivity is most pronounced in the direction perpendicular to this slip.

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“…This project focuses on the effects that changes in confining stress have on the transport properties of the fracture-matrix system. The confining stress has an impact on the fracture aperture and therefore on multiphase fluid transport properties (Barton et al, 1985, Gentier et al, 1997. We propose to quantify the changes in fracture porosity and saturation distribution under steady and non-steady flow in both the fracture and the adjoining matrix.…”

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confidence: 99%

Multi-Phase Fracture-Matrix Interactions Under Stress Changes

Grader¹,

Halleck²,

Alvarado³

et al. 2002

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The main objectives of this project are to quantify the changes in fracture porosity and multiphase transport properties as a function of confining stress. These changes will be integrated into conceptual and numerical models that will improve our ability to predict and optimize fluid transport in fractured system. This report details our progress on a. developing the direct experimental measurements of fracture aperture and topology using high-resolution x-ray microtomography, b. modeling of fracture permeability in the presence of asperities and confining stress, and c. simulation of two-phase fluid flow in a fracture and a layered matrix.The three-dimensional surface that describes the large-scale structure of the fracture in the porous medium can be determined using x-ray micro-tomography with significant accuracy. The distribution of fracture aperture is a difficult issue that we are studying and developing methods of quantification. The difficulties are both numerical and conceptual. Numerically, the threedimensional data sets include millions, and sometimes, billions of points, and pose a computational challenge. The conceptual difficulties derive from the rough nature of the fracture surfaces, and the heterogeneous nature of the rock matrix. However, the high-resolution obtained by the imaging system provides us a much needed measuring environment on rock samples that are subjected to simultaneous fluid flow and confining stress. Pilot multi-phase experiments have been performed, proving the ability to detect two phases in certain large fractures.The absolute permeability of a fracture depends on the behavior of the asperities that keep it open. A model is being developed that predicts the permeability and average aperture of a fracture as a function of time under steady flow of water including the pressure solution at the asperity contact points.

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Mapping fracture aperture as a function of normal stress using a combination of casting, image analysis and modeling techniques

Cited by 14 publications

References 2 publications

Fracture aperture reconstruction and determination of hydrological properties: a case study at Draix (French Alps)

Fracture aperture reconstruction and determination of hydrological properties: a case study at Draix (French Alps)

Relationship Between the Orientation of Maximum Permeability and Intermediate Principal Stress in Fractured Rocks

Multi-Phase Fracture-Matrix Interactions Under Stress Changes

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