Modelling and inferring fracture curvature from borehole GPR data: A case study from the Bedretto Laboratory, Switzerland
Open access
Date
2023Type
- Journal Article
ETH Bibliography
yes
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Abstract
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. Show more
Permanent link
https://doi.org/10.3929/ethz-b-000652299Publication status
publishedExternal links
Journal / series
Near Surface GeophysicsPublisher
WileySubject
faults; fracture; imaging; modelling; travel-timeOrganisational unit
02334 - BULGG - Bedretto Underground Lab / BULGG - Bedretto Underground Lab03476 - Giardini, Domenico / Giardini, Domenico
03953 - Robertsson, Johan / Robertsson, Johan
Funding
197366 - Characterizing and understanding Enhanced Geothermal Systems (EGS) - novel tools and applications in a deep underground laboratory (SNF)
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ETH Bibliography
yes
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