A travel time based hydraulic tomographic approach

Abstract

[1] Hydraulic tomography is a method to identify the three-dimensional spatial distribution of hydraulic properties in the subsurface. We propose a tomographic approach providing the inversion of travel times of hydraulic or pneumatic tests conducted in a tomographic array. The inversion is based on the relation between the peak time of a recorded transient pressure curve and the diffusivity of the investigated system. The development of a transformation factor enables the inversion of further travel times besides the peak time of a transient curve. As the early travel times of the curve are mainly related to preferential flow features while the inversion based on late travel times are reflecting an integral behavior, it can be assumed that the different inversion results reflect the properties of the overall system. By comparing the different reconstructions the system interpretation therefore becomes more comprehensive and reliable. Furthermore, the similarity of the proposed hydraulic tomographic approach to seismic travel time tomography allows us to apply the inversion algorithms which are used for seismic tomography. We therefore apply the method of staggered grids, which enables to refine the grid resulting in a higher nominal resolution, to data from a set of interference tests arranged in a tomographic array. The tests were conducted in an unsaturated fractured sandstone cylinder in the laboratory. The three-dimensional reconstructions of the diffusivity distribution are found to be highly reliable and robust. In particular, the mapped fracture of the sandstone cylinder coincides with our reconstructed diffusivity distribution.

A review of model applications for structured soils: a) Water flow and tracer transport

“…A 3D hydraulic tomography method, i.e., inversion of travel times of transient pressure propagation measured in hydraulic and pneumatic tests in an unsaturated fractured sandstone core, was used to estimate the local hydraulic property distribution and diffusivity (Brauchler et al, 2003). Other hydrogeophysical techniques include self potential, ground penetrating radar, induced polarization, electrical resistivity tomography, electromagnetic induction, microwave radiometry, and time domain reflectometry (TDR) (Vereecken et al, 2004).…”

Rapid field application of hydraulic tomography for resolving aquifer heterogeneity in unconsolidated sediments

“…Based on a travel time inversion scheme proposed by Brauchler et al [2003], they reconstructed the 2-D diffusivity distribution of the aquifer. Brauchler et al [2011] further developed the inversion approach and inverted cross-well interference slug tests with a travel time and attenuation based inversion scheme.…”

Joint interpretation of sequential pumping tests in unconfined aquifers

“…They include numerical studies [e.g., Gottlieb and Dietrich, 1995;Yeh and Liu, 2000;Bohling et al, 2002;Yeh, 2005, 2006;Fienen et al, 2008;Ni and Yeh, 2008;Castagna and Bellin, 2009;Xiang et al, 2009;Liu and Kitanidis, 2011], followed by laboratory sandbox studies [e.g., Liu et al, 2002;Brauchler et al, 2003;Illman et al, 2007;Liu et al, 2007;Illman et al, 2008;Yin and Illman, 2009;Illman et al, 2010;Berg and Illman, 2011a;Illman et al, 2012] and then experimental field studies [e.g. Bohling et al, 2007;Li et al, 2007;Straface et al, 2007;Cardiff et al, 2009;Illman et al, 2009;Berg and Illman, 2011b;Brauchler et al, 2011;Huang et al, 2011].…”