X-ray CT based numerical analysis of fracture flow for core samples under various confining pressures

Watanabe, Noriaki; Ishibashi, Takaharu; Ohsaki, Yutaka; Tsuchiya, Yoshihiro; Tamagawa, Tetsuya; Hirano, Nobuo; Okabe, Hiroshi; Tsuchiya, Noriyoshi

doi:10.1016/j.enggeo.2011.09.010

Cited by 65 publications

(46 citation statements)

References 29 publications

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“…However, they generally have the advantage of lower scanning times and are more flexible in terms of sample/equipment weights and sizes (Watanabe et al, 2011). Currently, medical CT scanners represent the most economical option to conduct such experiments and also provide, particularly in regard to their importance in medicine, a good accessibility.…”

Section: Introductionmentioning

confidence: 99%

“…Considering this study and further information provided in Table 1, most of the used fracture geometries can be assumed to be not directly correlated to the actual fracture geometries under loading conditions used for validation. For this reason, more recent studies introduced X-ray computed tomography (CT) that enables the scanning of in situ conditions during the experiment within the sample and creates "real-time" images of the fracture (Watanabe et al, 2011.…”

Section: Introductionmentioning

confidence: 99%

“…In the past, in situ imaging of experiments based on CT technologies was applied to a wide range of studies including geomechanical behavior of fractures (Re and Scavia, 1999), evaluations of triaxial tests (Feng et al, 2004;Ge et al, 2001;Lenoir et al, 2007;Ren and Ge, 2004;Vinegar et al, 1991;Zhou et al, 2008), shear tests (Tatone and Grasselli, 2015), sand production experiments (Santos et al, 2010) as well as various single-/multi-phase core-flooding experiments in fractured and unfractured rocks (Huo and Benson, 2015;Krevor et al, 2012;Oh et al, 2013;Perrin and Benson, 2010;Pini and Benson, 2013;Pini et al, 2012;Rangel-German et al, 2006;Schembre and Kovscek, 2003;Shi et al, 2009;Watanabe et al, 2011). CT technology generally represents a 3-D non-destructive method to image material contrasts in high resolution and, therefore, is well suited to reproduce dynamic processes in situ and in "real time".…”

Section: Introductionmentioning

confidence: 99%

“…Considering a transect perpendicular to the fracture plane, there are generally four methods to calibrate apertures caused by the fracture-related density anomaly (Ketcham and Carlson, 2001;. (1) The peak height (PH) method is based on the gap between the idealized matrix density and the negative peak of the anomaly, which was successfully applied by Watanabe et al (2011) but typically is more applicable for homo- geneous materials . The PH method requires a careful calibration.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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“…Integrated application of combined micro-CT characterization and process monitoring, with modelling could demonstrate the importance of rock heterogeneity (porosity, hydraulic conductivity, and diffusivity) in fluid transport processes (Kumar et al, 2010a;Kumar et al, 2010b;Watanabe et al, 2011a;Watanabe et al, 2011b). The petrophysical features of reservoir rocks can therefore be studied not only in the context of fluid flow but also as means of evaluating reservoir quality (Carlson, 2006).…”

Section:  Fluid Flow Analysismentioning

confidence: 99%

High-resolution X-ray computed tomography in geosciences: A review of the current technology and applications

Cnudde

Boone

2013

Earth-Science Reviews

1,236

700

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Please cite this article as: Cnudde, V., Boone, M.N., "High-resolution X-ray computed tomography in geosciences: a review of the current technology and applications", Earth Science Reviews (2013Reviews ( ), doi: 10.1016Reviews ( /j.earscirev.2013 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.A C C E P T E D M A N U S C R I P T AbstractHigh-resolution X-ray Computed Tomography (HRXCT) or micro-CT (µCT) is a frequently used non-destructive 3D imaging and analysis technique for the investigation of internal structures of a large variety of objects, including geomaterials. Although the possibilities of X-ray micro-CT are becoming better appreciated in earth science research, the demands on this technique are also approaching certain physical limitations. As such, there remains a lot of research to be done in order to solve all the technical problems that occur when higher demands are put on the technique. In this paper, a review of the principle, the advantages and limitations of X-ray CT itself are presented, together with an overview of some current applications of micro-CT in geosciences. One of the main advantages of this technique is the fact that it is a non-destructive characterization technique which allows 4D monitoring of internal structural changes at resolutions down to a few hundred nanometers. Limitations of this technique are the operator dependency for the 3D image analysis from the reconstructed data, the discretations effects and possible imaging artefacts. Driven by the technological and computational progress, the technique is continuously growing as an analysis tool in geosciences and is becoming one of the standard techniques, as is shown by the large and still increasing number of publications in this research area. It is foreseen that this number will continue to rise, and micro-CT will become an indispensable technique in the field of geosciences.

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Beyond‐laboratory‐scale prediction for channeling flows through subsurface rock fractures with heterogeneous aperture distributions revealed by laboratory evaluation

et al. 2015

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The present study evaluates aperture distributions and fluid flow characteristics for variously sized laboratory-scale granite fractures under confining stress. As a significant result of the laboratory investigation, the contact area in fracture plane was found to be virtually independent of scale. By combining this characteristic with the self-affine fractal nature of fracture surfaces, a novel method for predicting fracture aperture distributions beyond laboratory scale is developed. Validity of this method is revealed through reproduction of the results of laboratory investigation and the maximum aperture-fracture length relations, which are reported in the literature, for natural fractures. The present study finally predicts conceivable scale dependencies of fluid flows through joints (fractures without shear displacement) and faults (fractures with shear displacement). Both joint and fault aperture distributions are characterized by a scale-independent contact area, a scale-dependent geometric mean, and a scale-independent geometric standard deviation of aperture. The contact areas for joints and faults are approximately 60% and 40%. Changes in the geometric means of joint and fault apertures (μm), e m, joint and e m, fault , with fracture length (m), l, are approximated by e m, joint = 1 × 10 2 l 0.1 and e m, fault = 1 × 10 3 l 0.7 , whereas the geometric standard deviations of both joint and fault apertures are approximately 3. Fluid flows through both joints and faults are characterized by formations of preferential flow paths (i.e., channeling flows) with scale-independent flow areas of approximately 10%, whereas the joint and fault permeabilities (m 2 ), k joint and k fault , are scale dependent and are approximated as k joint = 1 × 10 À12 l 0.2 and k fault = 1 × 10 À8 l 1.1 .

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X-ray CT based numerical analysis of fracture flow for core samples under various confining pressures

Cited by 65 publications

References 29 publications

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

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

High-resolution X-ray computed tomography in geosciences: A review of the current technology and applications

Beyond‐laboratory‐scale prediction for channeling flows through subsurface rock fractures with heterogeneous aperture distributions revealed by laboratory evaluation

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