HR: 0830h
AN: H21D-0867    [PDF]
TI: Hydraulic Travel Time Tomography Appraisal Using Synthetic Data Sets
AU: * Brauchler, R
EM: ralf.brauchler@uni-tuebingen.de
AF: Center for Apllied Geoscience, University of Tuebingen, Sigwartstrasse 10, Tuebingen, 72076 Germany
AU: Cheng, J
EM: chengj@geo.tamu.edu
AF: Department of Geology and Geophysics, Texas A\&M University, MS 3115, College Station, TX 77843-3115 United States
AU: Dietrich, P
EM: peter.dietrich@uni-tuebingen.de
AF: Center for Apllied Geoscience, University of Tuebingen, Sigwartstrasse 10, Tuebingen, 72076 Germany
AU: Everett, M
EM: everett@geo.tamu.edu
AF: Department of Geology and Geophysics, Texas A\&M University, MS 3115, College Station, TX 77843-3115 United States
AU: Johnson, B
EM: johnson@geo.tamu.edu
AF: Department of Geology and Geophysics, Texas A\&M University, MS 3115, College Station, TX 77843-3115 United States
AB: Hydraulic tomography is an aquifer characterization method allowing the two and three dimensional spatial identification of hydraulic properties in the subsurface. Such information is essential for rigorous analysis of a variety of engineering, geotechnical and hydrogeological problems within the context of water resources management. We propose a tomographic approach providing the inversion of travel times of multiwell slug tests. The inversion is based on the relation between the travel times of a recorded transient pressure curve and the diffusivity of the geological medium. Usually, just one value of a measured hydraulic signal, mostly the peak time, is used as the data for the inversion in order to reconstruct the diffusivity field of the investigated system. This situation is not satisfying because much information is lost. Therefore, we have developed a transformation factor allowing to apply our approach to several travel times characterizing each signal. Thereby, each travel time is inverted separately. The main focus is to appraise the influence of the various travel times on the inversion results. It can be assumed that early travel times are dominated by preferential flow along fast, high permeability paths, while the inversion results based on late travel times reflect an integration of the received signal over many flow paths. Synthetic data sets were created using the Finite Element Heat and Mass Transfer Code (FEHM) from Los Alamos National Laboratory. The data base of the inversion comprises simulated slug tests, in which the position of the sources (injection ports) and the receivers (observation ports) isolated with packers, are varied between the tests. We also investigate the effects of input parameters such as the number of source-receiver positions used, borehole storage and permeability distribution. The hydraulic tomography appraisal shows a strong dependence of the inversion results on the used travel times and input parameters. Results of the inversion of the synthetic data sets demonstrates the effectiveness of the proposed technique. In particular, the reconstruction of a layered geological medium including a vertical fault is shown.
DE: 1829 Groundwater hydrology
SC: Hydrology [H]
MN: 2003 Fall Meeting