On the applicability of connectivity metrics to rough fractures under normal stress

Javanmard, Hoda; Saar, Martin O.; Vogler, Daniel

doi:10.1016/j.advwatres.2022.104122

Cited by 6 publications

(16 citation statements)

References 76 publications

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“…Related modifications were later presented in Javanmard et al. (2022) with respect to percolation theory. The individual steps of the workflow, from the fracture generation (Figure 4b) to the identified channels, are vividly illustrated using a base case, a 3D NS realization, and the volume flow as a critical variable (Figure 4).…”

Section: Channelingmentioning

confidence: 97%

“…The developed workflow was inspired by the 3D work of Ebrahimi et al (2014) and the 2D work of Le Goc et al (2010) and was first presented in Egert (2021) and Egert et al (2021). Related modifications were later presented in Javanmard et al (2022) with respect to percolation theory. The individual steps of the workflow, from the fracture generation (Figure 4b) to the identified channels, are vividly illustrated using a base case, a 3D NS realization, and the volume flow as a critical variable (Figure 4).…”

Section: Channel and Connectivity Identification Workflowmentioning

confidence: 99%

“…Tang et al (2019) evaluated the channeling characteristics and transport-related properties in pore-scale heterogeneous media. Javanmard et al (2022) compared different channel connectivity indicators regarding their applicability under normal stress conditions. In this way, several different indicators and approaches have been investigated, with all studies being limited to simple and planar 2D geometries, small flow velocities, and/or linear flow laws.…”

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confidence: 99%

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Spatial Characterization of Channeling in Sheared Rough‐Walled Fractures in the Transition to Nonlinear Fluid Flow

Egert,

Nitschke,

Gholami Korzani

et al. 2023

Water Resources Research

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Accurate quantification of spatially resolved fluid flow within fractures is crucial for successful reservoir development, such as Enhanced Geothermal Systems. This study presents an innovative workflow designed to model and characterize preferential flow paths (channels) within rough‐walled shear fractures. A set of 30 rough‐walled self‐affine fractures, all possessing identical roughness characteristics, is stochastically generated. By solving the nonlinear Navier‐Stokes equations in 420 individual realizations, the transition from linear to nonlinear flow regimes and the two extreme flow directions perpendicular and parallel to the shearing are numerically captured. A distinguishing feature of this approach is its comprehensive statistical analysis, which encompasses both the geometric and transport properties of flow paths in the non‐simplified three‐dimensional fractured void space under typical geothermal flow conditions. In a perpendicular orientation of flow and shearing, fluid flow exhibits pronounced localization, with more than one‐third of the volumetric flow concentrated within 15% of the fracture volume. In contrast, parallel to the shearing, a complex pattern of individual tortuous channels emerges, with flow occurring in 22% of the void space. Nonlinear effects primarily manifest outside these channels, suggesting that complex flow phenomena may dominate irregular fracture structures, such as contact zones or asperities. In the parallel case, increased flow rates lead to an amplification of channeling processes resulting in less affected volume and diminished tortuosity of the main flow path, while in perpendicular orientation nonlinear effects are only of minor importance. The small‐scale flow regime of both extreme cases tends to converge with increasing flow rates.

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Section: Channelingmentioning

confidence: 97%

Section: Channel and Connectivity Identification Workflowmentioning

confidence: 99%

mentioning

confidence: 99%

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Spatial Characterization of Channeling in Sheared Rough‐Walled Fractures in the Transition to Nonlinear Fluid Flow

Egert,

Nitschke,

Gholami Korzani

et al. 2023

Water Resources Research

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“…On the one hand, the cubic law has been correlated, and the fracture permeability can be directly calculated by incorporating varied geometrical parameters; on the other hand, quantified scaling functions such as the relationship between fracture normal stiffness and fracture permeability has been proposed, as such the fracture permeability can be indirectly estimated through the normal stiffness, which can be remotely detected with geophysical methods. However, these studies are mainly based on laboratory experiments and numerical simulations, which in general are costly and computationally inefficient, and the results based on a single statistical parameter do not fully reflect the effective permeability of the heterogeneous fracture aperture field [16]. Therefore, some researchers have proposed the use of percolation theory to estimate the permeability of heterogeneous porous media.…”

Section: Introductionmentioning

confidence: 99%

“…The two types of connectivity metrics can be linked; however, the relations are extremely complex. With the above research basis, Javarmand et al [16] recently successfully applied static connectivity metrics for the first time based on percolation theory to estimate the permeability of rough deformed fractures. For three commonly used connectivity metrics, the accuracy of the permeability prediction was 72%, 55%, and 63%, respectively, which needs to be further improved.…”

Section: Introductionmentioning

confidence: 99%

A Connectivity Metrics-Based Approach for the Prediction of Stress-Dependent Fracture Permeability

Deng,

Shang,

2024

Water

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Rapid and accurate assessment of fracture permeability is critical for subsurface resource and energy development as well as rock engineering stability. Fracture permeability deviates from the classical cubic law under the effect of roughness, geological stress, as well as mining-induced stress. Conventional laboratory tests and numerical simulations are commonly costly and time-consuming, whereas the use of a connectivity metric based on percolation theory can quickly predict fracture permeability, but with relatively low accuracy. For this reason, we selected two static connectivity metrics with the highest and lowest prediction accuracy in previous studies, respectively, and proposed to revise and use them for fracture permeability estimation, considering the effect of isolated large-aperture regions within the fractures under increasing normal stress. Several hundred fractures with different fractal dimensions and mismatch lengths were numerically generated and deformed, and their permeability was calculated by the local cubic law (LCL). Based on the dataset, the connectivity metrics were counted using the revised approach, and the results show that, regardless of the connectivity metrics, the new model greatly improves the accuracy of permeability prediction compared to the pre-improved model, by at least 8% for different cutoff aperture thresholds.

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Influence of contact characteristics on nonlinear flow and eddy development in three-dimensional fractures under normal stress

Zhang,

Wang,

Yang

et al. 2024

Bull Eng Geol Environ

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On the applicability of connectivity metrics to rough fractures under normal stress

Cited by 6 publications

References 76 publications

Spatial Characterization of Channeling in Sheared Rough‐Walled Fractures in the Transition to Nonlinear Fluid Flow

Spatial Characterization of Channeling in Sheared Rough‐Walled Fractures in the Transition to Nonlinear Fluid Flow

A Connectivity Metrics-Based Approach for the Prediction of Stress-Dependent Fracture Permeability

Influence of contact characteristics on nonlinear flow and eddy development in three-dimensional fractures under normal stress

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