An inversion strategy for hydraulic tomography: Coupling travel time and amplitude inversion

We present a hydraulic tomographic inversion strategy with an emphasis on the reduction of ambiguity of hydraulic travel time inversion results and the separation of the estimated diffusivity values into hydraulic conductivity and specific storage. Our tomographic inversion strategy is tested by sim...

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Bibliographic Details
Published in:Journal of hydrology (Amsterdam) 2007-10, Vol.345 (3), p.184-198
Main Authors: Brauchler, R., Cheng, J.-T., Dietrich, P., Everett, M., Johnson, B., Liedl, R., Sauter, M.
Format: Article
Language:English
Subjects:
aquifers
Earth sciences
Earth, ocean, space
Exact sciences and technology
groundwater flow
hydraulic conductivity
Hydraulic tomography
hydraulic travel time tomography
Hydrogeology
Hydrogeophysics
hydrologic models
Hydrology. Hydrogeology
Inversion theory
mathematical models
MODFLOW-96 model
Multilevel interference slug tests
simulation models
tomography
Wellbore storage
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Summary:We present a hydraulic tomographic inversion strategy with an emphasis on the reduction of ambiguity of hydraulic travel time inversion results and the separation of the estimated diffusivity values into hydraulic conductivity and specific storage. Our tomographic inversion strategy is tested by simulated multilevel interference slug tests in which the positions of the sources (injection ports) and the receivers (observation ports) isolated with packers are varied. Simulations include the delaying effect of wellbore storage on travel times which are quantified and shown to be of increasing importance for shorter travel distances. For the reduction of ambiguity of travel time inversion, we use the full travel time data set, as well as smaller data subsets of specified source–receiver angles. The inversion results of data subsets show different resolution characteristics and improve the reliability of the interpretation. The travel time of a pressure pulse is a function of the diffusivity of the medium between the source and receiver. Thus, it is difficult to directly derive values for hydraulic conductivity and specific storage by inverting travel times. In order to overcome this limitation, we exploit the great computational efficiency of hydraulic travel time tomography to define the aquifer structure, which is then input into the underlying groundwater flow model MODFLOW-96. Finally, we perform a model calibration (amplitude inversion) using the automatic parameter estimator PEST, enabling us to separate diffusivity into its two components hydraulic conductivity and specific storage.
ISSN:0022-1694
1879-2707
DOI:10.1016/j.jhydrol.2007.08.011