Determination of aperture structure and fluid flow in a rock fracture by high‐resolution numerical modeling on the basis of a flow‐through experiment under confining pressure

Watanabe, Noriaki; Hirano, Nobuo; Tsuchiya, Noriyoshi

doi:10.1029/2006wr005411

Cited by 153 publications

(162 citation statements)

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“…Mean apertures of the sandstone sample are significantly lower and range between 0.031 and 0.024 mm (Huo and Benson, 2015). Nevertheless, with increasing stresses, hydraulic apertures of the granite fracture decrease from 0.009 to 0.003 mm (Watanabe et al, 2008) while hydraulic apertures of the sandstone fracture decrease from approximately 0.030 to 0.005 mm (Huo and Benson, 2015). These significant hydraulic differences of the samples appear to be caused by higher tortuosity as described by Tsang (1984) due to a higher roughness of the tensile granite fractures as compared with the smooth sandstone fracture.…”

Section: Comparisonmentioning

confidence: 99%

“…Although both rock types, Zenifim sandstone and granite, reveal similar matrix permeabilities (10 −18 to 10 −19 m 2 ), fluid flow experiments with the fractured sandstone obtain higher permeabilities (between 10 −14 and 10 −15 m 2 ) than granite experiments (between 10 −15 and 10 −17 m 2 ). Typically, mean apertures of mated tensile fractures in Inada granite should decrease from 0.071 to 0.065 mm, applying loading from 10 to 100 MPa (Watanabe et al, 2008). Mean apertures of the sandstone sample are significantly lower and range between 0.031 and 0.024 mm (Huo and Benson, 2015).…”

Section: Comparisonmentioning

confidence: 99%

“…However, they do not address residual changes as a result of mechanical deformation within the fracture, which can be addressed by subsequent unloading. Except the study by Watanabe et al (2008), who highlight qualitative insights into the flow structures, all other studies in Table 1 quantify and intend to validate simulated fracture flow. In a subsequent study which is not listed in Table 1, Watanabe et al (2009) applied a similar (non-quantitative) procedure for other fracture types.…”

Section: Introductionmentioning

confidence: 99%

“…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%

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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: Comparisonmentioning

confidence: 99%

Section: Comparisonmentioning

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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“…Diversos estudos (Watanabe et al, 2008;Becker e Tsoflias, 2010;Wang e Cardenas, 2014;Ishibashi et al, 2015) têm reportado a presença de caminhos preferenciais de alta condutividade hidráulica (channeling) que permitem o transporte de solutos em pequenas regiões da fratura com velocidade acima da velocidade média. Por isso, a modelagem do transporte de soluto necessita de uma caracterização precisa e acurada do campo de velocidades do escoamento dentro da fratura (Bodin et al, 2003).…”

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Migração de solutos em basalto fraturado: quantificação experimental em laboratório e validação matemática

Lucas¹

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A avaliação do risco a contaminação e a escolha de técnicas de remediação de poluentes em aquíferos fraturados depende da quantificação dos fenômenos envolvidos no transporte de solutos. A geometria da fratura, usualmente caracterizada pela abertura, é o principal parâmetro que indiretamente controla o transporte nos aquíferos fraturados. A simplificação mais comum desse problema é assumir que as fraturas são um par de placas planas e paralelas, isto é, com uma abertura constante. No entanto, por causa do limitado número de trabalhos experimentais, não está esclarecida a adequabilidade do uso de uma abertura constante para simular o transporte conservativo em fraturas do Aquífero Serra Geral (ASG), Brasil. O objetivo deste trabalho é avaliar a influência da abertura de uma fratura natural do Aquífero Serra Geral sob o transporte conservativo de solutos. Uma amostra natural de basalto fraturado foi usada em um experimento hidráulico e de transporte de um traçador conservativo (escala de laboratório). O campo de abertura foi medido usando a técnica avançada, de alta resolução e tridimensional, chamada microtomografia computadorizada de raios-X. A concentração de traçador medida foi utilizada para validar uma solução analítica unidimensional da Equação de Advecção-dispersão (ADE). O desemprenho do ajuste da ADE às curvas de passagem experimentais foi avaliado para quatro diferentes tipos de aberturas constantes. Os resultados mostraram que o escoamento de água e o transporte de contaminantes pode ocorrer através de fraturas micrométricas, ocasionando, eventualmente, a contaminação do ASG. A abertura de balanço de massa é a única que pode ser chamada propriamente de "abertura equivalente". O uso de aberturas constantes na ADE não permitiu representar completamente o formato das curvas de passagem porque o campo de velocidade não é uniforme e intrinsicamente bidimensional. Portanto, na simulação do transporte deve-se incorporar a heterogeneidade da abertura da fratura.Palavras-chave: Advecção-dispersão, Breakthrough curve, Espectrofotometria, Lei Cúbica, Microtomografia de raios-X. The contamination risk assessment and the choice of suitable cleanup techniques for pollutants in fractured rock depends on the quantification of the transport phenomena. Fracture geometry often described by the apertures is the major parameter that controls indirectly solute transport in fractured rock. The simplest approach is describing fractures as a pair of smooth parallel plates with constant aperture. However, there is a lack of information about the suitability for using a constant aperture for the conservative solute transport prediction in a single fracture of Serra Geral Aquifer (SGA), Brazil. The aim of this work is to evaluate the effect of aperture variability in a natural single rough-walled fracture of Serra Geral Aquifer on conservative solute transport. A natural core of fractured basalt was used for a hydraulic and tracer tests (laboratory scale). The aperture field was measured using the advanced, high-resolution and tr...

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Flow‐dependence of matrix diffusion in highly heterogeneous rock fractures

Cvetković

Gotovac

2013

Water Resources Research

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[1] Diffusive mass transfer in rock fractures is strongly affected by fluid flow in addition to material properties. The flow-dependence of matrix diffusion is quantified by a random variable (''transport resistance'') denoted as b [T/L] and computed from the flow field by following advection trajectories. The numerical methodology for simulating fluid flow is mesh-free, using Fup basis functions. A generic statistical model is used for the transmissivity field, featuring three correlation structures: (i) highly connected non-multiGaussian; (ii) poorly connected (or disconnected) non-multi-Gaussian ; and (iii) multiGaussian. The moments of b are shown to be linear with distance, irrespective of the structure, after approximately 10 integral scales of ln T. Percentiles of b are found to be linear with the mean b when considering all three structures. Taking advantage of this property, a potentially useful relationship is presented between b percentiles and the fracture mean water residence time that integrates all structures with high variability; it can be used in discrete fracture network simulations where T statistical data on individual fractures are not available.Citation: Cvetkovic, V., and H. Gotovac (2013), Flow-dependence of matrix diffusion in highly heterogeneous rock fractures, Water Resour. Res., 49,[7587][7588][7589][7590][7591][7592][7593][7594][7595][7596][7597]

show abstract

Determination of aperture structure and fluid flow in a rock fracture by high‐resolution numerical modeling on the basis of a flow‐through experiment under confining pressure

Cited by 153 publications

References 35 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

Migração de solutos em basalto fraturado: quantificação experimental em laboratório e validação matemática

Flow‐dependence of matrix diffusion in highly heterogeneous rock fractures

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