377 research outputs found
Widen Field Test Pressure Data - P02 Experiment
No full textHydraulic tomography data from the crosswell pressure test P02.
The data are referenced in the paper:
Vasco, D. W., J. Doetsch, and R. Brauchler (2018). An extended trajectory-mechanics approach for calculating the path of a pressure transient: Hydraulic tomographic imaging, Water Resources Research, (submitted)
and in
Lochbuhler, T., J. Doetsch, R. Brauchler, and N. Linde (2013). Structure-coupled joint inversion of geophysical and hydrological data, Geophysics, 78, ID1-ID14, doi: 10.1190/GEO2012-0460.
Generalized focusing of time-lapse changes with applications to direct current and time-domain induced polarization inversions
No full textOften in geophysical monitoring experiments time-lapse inversion models vary too smoothly
with time, owing to the strong imprint of regularization. Several methods have been proposed
for focusing the spatiotemporal changes of the model parameters. In this study, we present two
generalizations of the minimum support norm, which favour compact time-lapse changes and
can be adapted to the specific problem requirements. Inversion results from synthetic direct
current resistivity models that mimic developing plumes show that the focusing scheme significantly improves size, shape and magnitude estimates of the time-lapse changes. Inversions
of the synthetic data also illustrate that the focused inversion gives robust results and that the
focusing settings are easily chosen. Inversions of full-decay time-domain induced polarization
(IP) field data from a CO2 monitoring injection experiment show that the focusing scheme
performs well for field data and inversions for all four Cole–Cole polarization parameters.
Our tests show that the generalized minimum support norms react in an intuitive and predictable
way to the norm settings, implying that they can be used in time-lapse experiments
for obtaining reliable and robust results
A multi-borehole 3-D ERT monitoring system for aquifer characterization using river flood events as a natural tracer
No full textI. Coscia, S. Greenhalgh, N. Linde, A. Green, T. Günther, J. Doetsch and T. Vogthttp://www.earthdoc.org/detail.php?pubid=40923http://www.eage.org/events/index.php?evp=3166&ActiveMenu=18&Opendivs=s3,s17&act=det&prev=&ses=110
Frühneuzeitliche Räume des Visuellen: Zur Medialität des Spiegels in Garcilaso de la Vegas Égloga II
No full textKramer K. Frühneuzeitliche Räume des Visuellen: Zur Medialität des Spiegels in Garcilaso de la Vegas Égloga II . In: Dünne J, Doetsch H, Lüdeke R, eds. Von Pilgerwegen, Schriftspuren und Blickpunkten. Raumpraktiken in medienhistorischer Perspektive . Würzburg: Königshausen & Neumann; 2004: 99-121
Hydrogeophysical studies in unrestored and restored river corridors of the Thur River, Switzerland
No full textNiklas Linde, Ilaria Coscia, Joseph A. Doetsch, Stewart A. Greenhalgh, Tobias Vogt, Philipp Schneider and Alan G. Greenhttp://www.earthdoc.org/detail.php?pubid=4074
Derivation of site-specific relationships between hydraulic parameters and p-wave velocities based on hydraulic and seismic tomography
No full textIn this study, hydraulic and seismic tomographic measurements were used to derive a site-specific relationship between the geophysical parameter p-wave velocity and the hydraulic parameters, diffusivity and specific storage. Our field study includes diffusivity tomograms derived from hydraulic travel time tomography, specific storage tomograms, derived from hydraulic attenuation tomography, and p-wave velocity tomograms, derived from seismic tomography. The tomographic inversion was performed in all three cases with the SIRT (Simultaneous Iterative Reconstruction Technique) algorithm, using a ray tracing technique with curved trajectories. The experimental set-up was designed such that the p-wave velocity tomogram overlaps the hydraulic tomograms by half. The experiments were performed at a wellcharacterized sand and gravel aquifer, located in the Leine River valley near Göttingen, Germany. Access to the shallow subsurface was provided by direct-push technology. The high spatial resolution of hydraulic and seismic tomography was exploited to derive representative site-specific relationships between the hydraulic and geophysical parameters, based on the area where geophysical and hydraulic tests were performed. The transformation of the p-wave velocities into hydraulic properties was undertaken using a k-means cluster analysis. Results demonstrate that the combination of hydraulic and geophysical tomographic data is a promising approach to improve hydrogeophysical site characterization
Anisotropic traveltime inversion of hard rock targets: Synthetic and Field Study at the Grimsel Test Site
No full textCivil Engineering and GeosciencesGeoscience and EngineeringIDEA Leagu
Direct current (DC) resistivity and induced polarization (IP) monitoring of active layer dynamics at high temporal resolution
No full textWith permafrost thawing and changes in active layer dynamics induced by climate change, interactions between biogeochemical and thermal processes in the ground are of great importance. Here, active layer dynamics have been monitored using direct current (DC) resistivity and induced polarization (IP) measurements at high temporal resolution and at a relatively large scale at a heath tundra site on Disko Island on the west coast of Greenland (69°N). At the field site, the active layer is disconnected from the deeper permafrost, due to isothermal springs in the region. Borehole sediment characteristics and subsurface temperatures supplemented the DC-IP measurements. A time-lapse DC-IP monitoring system has been acquiring at least six datasets per day on a 42-electrode profile with 0.5. m electrode spacing since July 2013. Remote control of the data acquisition system enables interactive adaptation of the measurement schedule, which is critically important to acquire data in the winter months, where extremely high contact resistances increase the demands on the resistivity meter. Data acquired during the freezing period of October 2013 to February 2014 clearly image the soil freezing as a strong increase in resistivity. While the freezing horizon generally moves deeper with time, some variations in the freezing depth are observed along the profile. Comparison with depth-specific soil temperature indicates an exponential relationship between resistivity and below-freezing temperature. Time-lapse inversions of the full-decay IP data indicate a decrease of normalized chargeability with freezing of the ground, which is the result of a decrease in the total unfrozen water and of the higher ion concentration in the pore-water. We conclude that DC-IP time-lapse measurements can non-intrusively and reliably image freezing patterns and their lateral variation on a 10-100. m scale that is difficult to sample by point measurements. In combination with laboratory experiments, the different patterns in resistivity and chargeability changes will enable the disentanglement of processes (e.g., fluid migration and freezing, advective and diffusive heat transport) occurring during freezing of the ground. The technology can be expanded to three dimensions and also to larger scale
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