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Fracture movie aspect ratio9/24/2023 ![]() 2017 Mazzella and Morrison 1974 Park 1991 Gunasekera et al. Geophysical observations can detect changes in electrical resistivity or elastic wave velocity that may reflect subsurface stress changes associated with hydraulic stimulation, earthquakes, or geothermal fluid production (Peacock et al. 1988) and characterize the transport behavior of fluid resources. These changes produce transitions in the patterns of fracture flow that in turn control the fault reactivation cycle (Sibson et al. In-situ stress is never constant during geoengineering developments or on the geological time scale, and consequently, the aperture distribution and associated hydraulic properties also must change in natural settings (e.g., Manga et al. 1979 Raven and Gale 1985 Thompson and Brown 1991 Watanabe et al. It is known that fracture permeability and preferential flow paths within fractures are controlled by the heterogeneous distribution of apertures, which can vary as stress changes (Krantz et al. The hydraulic properties of fractured geological formations have been of interest for many purposes such as developing fluid resources (e.g., geothermal fluids, shale oil, and groundwater), geological storage or disposal, and seismic events (fault reactivation and induced seismicity). The hydraulic-electrical-elastic relationships reported here may be beneficial for improving geophysical interpretations and may find applications in studies of seismogenic zones and geothermal reservoirs. Elastic wave velocity offers potential for detecting the transition between aperture-dependent flow and aperture-independent flow, and resistivity is sensitive to the state of connection of the fracture flow. We also are able to categorize fracture flow patterns as aperture-dependent, aperture-independent, or disconnected flows, with transitions at specific stress levels. This discrepancy arises from the different sensitivities of these quantities to microstructure: velocity is sensitive to the spatial distribution of asperity contacts, whereas permeability and resistivity are insensitive to contact distribution, but instead are controlled by fluid connectivity. We show that electrical resistivity is linked with permeability and flow area regardless of fracture roughness, whereas elastic wave velocity is roughness-dependent. Our lattice Boltzmann simulation reveals transitions in three-dimensional flow paths, and finite-element modeling enables us to investigate the corresponding evolution of geophysical properties. ![]() This study explores simultaneous changes in hydraulic and geophysical properties of natural rock fractures with increasing normal stress and correlates these property changes through coupling experiments and digital fracture simulations. Geophysical observations are promising tools for remote determination of subsurface hydraulic properties however, quantitative interpretations are hampered by the paucity of relevant geophysical data for fractured rock masses. ![]() Monitoring the hydraulic properties within subsurface fractures is vitally important in the contexts of geoengineering developments and seismicity.
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