X-ray CT and hydraulic evidence for a relationship between fracture conductivity and adjacent matrix porosity

Karpyn, Zuleima T.; Alajmi, Abdullah F.; Radaelli, F.; Halleck, P.M.; Grader, A.S.

doi:10.1016/j.enggeo.2008.06.017

Cited by 84 publications

(38 citation statements)

References 17 publications

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“…Due to the missing appropriate validation experiments and the negligible matrix flow, possible fracture-matrix interaction is not further discussed in this study and can be considered as uninfluential artifacts of the matrix material. Nevertheless, the MSMA method can provide a promising approach to simulate such issues, especially considering laminated sandstones, which were experimentally investigated in the past (Clavaud et al, 2008;Grader et al, 2013;Karpyn et al, 2009). Indeed, this method can be erroneous for heterogeneous rocks such as granite, but Watanabe et al (2011) found that affectations of locally resulting non-real apertures in the matrix are marginal.…”

Section: Simulationmentioning

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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Section: Simulationmentioning

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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“…A number of destructive techniques have previously been used to evaluate the roughness of natural fractures in rock, including measurements using stylus profilemeters [7,20] and surface laser scanning [11,12,21,22]. Nuclear magnetic resonance imaging [4,23] and CT scanning [24][25][26][27][28] are two methods that have been used to obtain detailed fracture geometries without destroying the original sample. All of these methods have shown that fractures are complex, and many have shown that the fracture structure is well described by fractal geometry [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Numerical simulations examining the relationship between wall-roughness and fluid flow in rock fractures

Crandall

Bromhal

Karpyn

2010

International Journal of Rock Mechanics and Mining Sciences

129

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“…To calculate the missing attenuation due to the presence of a fracture; data cropping, classification, and identification of fracture features are needed (Karpyn, 2009);. The missing attenuation is calculated using Eq.…”

Section: Methods For Measuring Fracture Aperture Using Ct Scanningmentioning

confidence: 99%

Investigating Aperture-Based Stress-Dependent Permeability and Capillary Pressure in Rock Fractures

Huo

Benson

2014

All Days

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Understanding multi-phase fluid flow behavior in fractured porous media is crucial for developing fractured hydrocarbon reservoirs, implementing hydraulic fracturing, and predicting potential leakage in gas and CO 2 storage. The goal of this research is to investigate stress-dependent permeability and capillary pressure in rock fractures. Laboratory measurements of fracture aperture distributions have been made using CT scanning under various conditions of effective stress. By applying the stress-dependent aperture data, numerical simulation is employed to model the change of permeability and capillary pressure in the rock fracture as a function of the effective stress.The stress-dependent aperture distribution data demonstrates that increasing stress results in two effects: (1); the mean aperture will decrease; (2); the variance of aperture distribution will increase. Experimental results show that permeability will drop by 73% when effective stress increases from 0.34MPa to 22.06MPa. As the variance of aperture distribution increases with stress, the plateau area of the capillary pressure curve tends to grow steeper, indicating that capillary behavior changes from more fracture-like to more porous media-like. The impacts of mean and variance of aperture distributions on permeability and capillary pressure are separately analyzed. The mean aperture decrease will reduce permeability and increase entry pressure. The variance increase will reduce permeability, the pore size distribution index and entry pressure. By analyzing the stress-dependent mean and variance of aperture distributions, this paper provides a more straightforward way for estimating stress-dependent permeability and capillary pressure in rock fractures.

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X-ray CT and hydraulic evidence for a relationship between fracture conductivity and adjacent matrix porosity

Cited by 84 publications

References 17 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

Numerical simulations examining the relationship between wall-roughness and fluid flow in rock fractures

Investigating Aperture-Based Stress-Dependent Permeability and Capillary Pressure in Rock Fractures

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