Four-dimensional tracer flow reconstruction in fractured rock through borehole ground-penetrating radar (GPR) monitoring

Giertzuch, Peter-Lasse; Doetsch, Joseph; Shakas, Alexis; Jalali, Mohammadreza; Brixel, Bernard; Maurer, Hansruedi

doi:10.5194/se-12-1497-2021

Cited by 6 publications

(4 citation statements)

References 38 publications

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“…Still, even if such successful local validation is possible, there are no other independent measurements available to confirm the validity of the inverted complete DFN structure and its probability. Geophysical measurements such as seismic data (Doetsch et al, 2020) or ground-penetrating radar (Giertzuch et al, 2021a) were able to characterize the ISC volume on a decameterscale and identify the persistent structures and the highly fractured zone, however, they could not delineate or specify the properties of single flow paths.…”

Section: Comparison With Other Studiesmentioning

confidence: 99%

Characterization of the highly fractured zone at the Grimsel test site based on hydraulic tomography

Ringel

Jalali

Bayer

2022

Preprint

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Abstract. In this study, we infer the structural and hydraulic properties of the highly fractured zone at the Grimsel test site in Switzerland by a stochastic inversion method. The fractured rock is modeled directly as a discrete fracture network (DFN) within an impermeable rock matrix. Cross-hole transient pressure signals recorded from constant rate injection tests in different intervals provide the basis for the herein presented first field application of the inversion. The experimental setup is realized by a multi-packer system. The geological mapping of the structures intercepted by boreholes and data from previous studies that were undertaken as part of the in-situ stimulation and circulation (ISC) experiments facilitate the setup of the site-dependent conceptual and forward model. The inversion results show that two preferential flow paths between the two boreholes can be distinguished. One is dominated by fractures with large hydraulic apertures while the other path consists mainly of fractures with a smaller aperture. The probability of fractures linking both flow paths increases the closer we are at the second injection borehole. The results accord with the findings from other studies conducted at the site during the ISC measurement campaign and add new insights about the highly fractured zone at the prominent study site.

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Section: Comparison With Other Studiesmentioning

confidence: 99%

Characterization of the highly fractured zone at the Grimsel test site based on hydraulic tomography

Ringel

Jalali

Bayer

2022

Preprint

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“…GPR has been widely used for imaging fracture networks and detecting permeable fractures in various hydrogeological, geotechnical and nuclear waste‐related applications (see Molron et al., 2020; Slob et al., 2010, for an overview). In certain cases, EM waves with wavelengths at the metre‐scale can resolve fractures with sub‐millimetre aperture (i.e., thin‐bed response) due to the high dielectric contrast between the host rock and fracture filling (Dorn et al., 2012; Day‐Lewis et al., 2017; Glover, 2015; Giertzuch et al., 2021). Properties such as fracture size, local orientation (i.e., curvature), position, extent, aperture and filling, play an important role in the wave‐scattering response at the fracture interface, allowing to infer fracture properties from GPR data.…”

Section: Introductionmentioning

confidence: 99%

“…GPR has been widely used for imaging fracture networks and detecting permeable fractures in various hydrogeological, geotechnical and nuclear waste-related applications (see Molron et al, 2020;Slob et al, 2010, for an overview). In certain cases, EM waves with wavelengths at the metre-scale can resolve fractures with sub-millimetre aperture (i.e., thin-bed response) due to the high dielectric contrast between the host rock and fracture filling (Dorn et al, 2012;Day-Lewis et al, 2017;Glover, 2015;Giertzuch et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Modelling and inferring fracture curvature from borehole GPR data: A case study from the Bedretto Laboratory, Switzerland

Escallon,

Shakas,

Maurer

2023

Near Surface Geophysics

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Fracture curvature has been observed from the millimetre to the kilometre scales. Nevertheless, characterizing curvature remains challenging due to data sparsity and geometric ambiguities. As a result, most numerical models often assume planar fractures to ease computations. To address this limitation, we present a novel approach for inferring fracture geometry from travel‐time data of electromagnetic or seismic waves. Our model utilizes co‐kriging interpolation of control points in a three‐dimensional surface mesh to simulate fracture curvature effectively, resulting in an unstructured triangular grid. We then refine the fracture surface into a structured grid with equidistant elements so that both small‐scale heterogeneities and large‐scale curvature can be modelled. To constrain the fracture geometry, we perform a deterministic travel‐time inversion to optimally place these control points. We validate our methodology with synthetic data and address its limitations. Finally, we infer the geometry of a large (more than 200 m) fracture observed in single‐hole ground‐penetrating radar field data. The fracture surface closely agrees with borehole televiewer observations and is also constrained far from the boreholes. Our modelling approach can be trivially adapted to multi‐offset ground‐penetrating radar or active seismic data.

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“… 2017 ) or ground-penetrating radar (Giertzuch et al. 2021 ; Steelman et al. 2017 ) have been applied in similar contexts, the focus of this review is on TL-ERT since this technique is cost-efficient, robust and readily deployable for large-scale monitoring.…”

Section: Introductionmentioning

confidence: 99%

A Review on Applications of Time-Lapse Electrical Resistivity Tomography Over the Last 30 Years : Perspectives for Mining Waste Monitoring

et al. 2022

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Mining operations generate large amounts of wastes which are usually stored into large-scale storage facilities which pose major environmental concerns and must be properly monitored to manage the risk of catastrophic failures and also to control the generation of contaminated mine drainage. In this context, non-invasive monitoring techniques such as time-lapse electrical resistivity tomography (TL-ERT) are promising since they provide large-scale subsurface information that complements surface observations (walkover, aerial photogrammetry or remote sensing) and traditional monitoring tools, which often sample a tiny proportion of the mining waste storage facilities. The purposes of this review are as follows: (i) to understand the current state of research on TL-ERT for various applications; (ii) to create a reference library for future research on TL-ERT and geoelectrical monitoring mining waste; and (iii) to identify promising areas of development and future research needs on this issue according to our experience. This review describes the theoretical basis of geoelectrical monitoring and provides an overview of TL-ERT applications and developments over the last 30 years from a database of over 650 case studies, not limited to mining operations (e.g., landslide, permafrost). In particular, the review focuses on the applications of ERT for mining waste characterization and monitoring and a database of 150 case studies is used to identify promising applications for long-term autonomous geoelectrical monitoring of the geotechnical and geochemical stability of mining wastes. Potential challenges that could emerge from a broader adoption of TL-ERT monitoring for mining wastes are discussed. The review also considers recent advances in instrumentation, data acquisition, processing and interpretation for long-term monitoring and draws future research perspectives and promising avenues which could help improve the design and accuracy of future geoelectric monitoring programs in mining wastes.

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Four-dimensional tracer flow reconstruction in fractured rock through borehole ground-penetrating radar (GPR) monitoring

Cited by 6 publications

References 38 publications

Characterization of the highly fractured zone at the Grimsel test site based on hydraulic tomography

Characterization of the highly fractured zone at the Grimsel test site based on hydraulic tomography

Modelling and inferring fracture curvature from borehole GPR data: A case study from the Bedretto Laboratory, Switzerland

A Review on Applications of Time-Lapse Electrical Resistivity Tomography Over the Last 30 Years : Perspectives for Mining Waste Monitoring

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