An Application of Hydraulic Tomography to a Large‐Scale Fractured Granite Site, Mizunami, Japan

Abstract

While hydraulic tomography (HT) is a mature aquifer characterization technology, its applications to characterize hydrogeology of kilometer-scale fault and fracture zones are rare. This paper sequentially analyzes datasets from two new pumping tests as well as those from two previous pumping tests analyzed by Illman et al. (2009) at a fractured granite site in Mizunami, Japan. Results of this analysis show that datasets from two previous pumping tests at one side of a fault zone as used in the previous study led to inaccurate mapping of fracture and fault zones. Inclusion of the datasets from the two new pumping tests (one of which was conducted on the other side of the fault) yields locations of the fault zone consistent with those based on geological mapping. The new datasets also produce a detailed image of the irregular fault zone, which is not available from geological investigation alone and the previous study. As a result, we conclude that if prior knowledge about geological structures at a field site is considered during the design of HT surveys, valuable non-redundant datasets about the fracture and fault zones can be collected. Only with these non-redundant data sets, can HT then be a viable and robust tool for delineating fracture and fault distributions over kilometer scales, even when only a limited number of boreholes are available. In essence, this paper proves that HT is a new tool for geologists, geophysicists, and engineers for mapping large-scale fracture and fault zone distributions.

Equivalence of Discrete Fracture Network and Porous Media Models by Hydraulic Tomography

“…An accurate mapping of a sparse DFN model requires extremely a high density of monitoring wells. On the other hand, in the case of DFNs with high fracture intensities, not only the representative fractures can be characterized but also a reasonable distribution of K and S s of EPM can be obtained, which can be referred to as fracture zones, through limited number of monitoring wells (Zha et al, , ).…”

“…Over the past decades, the power of HT for mapping heterogeneity in porous media has been unequivocally demonstrated by many (Berg & Illman, , , ; Huang et al, ; Illman et al, ; Kuhlman et al, ; Liu et al, , , ; Tso et al, ; Wen et al, ; Ye et al, ; Zha et al, ; Zhu & Yeh, ). For mapping fractures in geologic media, encouraging HT results have been obtained in a few laboratory and field studies (Brauchler et al, ; Castagna et al, ; Illman, ; Illman et al, ; Sharmeen et al, ; Zha et al, , ), yet many more studies are necessary to further assess HT's viability.…”

Synthetic fracture network characterization with transdimensional inversion

“…Here, pressure or tracer signals are recorded between different sources and receivers (e.g., multiple well screens) and the data are inverted to image the spatial heterogeneity in the subsurface. Illman [] reviewed the state‐of‐the art in hydraulic and pneumatic tomography in fractured rock, with successful applications to synthetic models [ Hao et al ., ; Ni and Yeh , ; Zha et al ., ], laboratory [ Sharmeen et al ., ], and field cases [ Meier et al ., ; Vesselinov et al ., , ; Franssen and Gómez‐Hernández , ; Brauchler et al ., ; Ni and Yeh , ; Illman et al ., ; Castagna et al ., ; Zha et al ., ]. All these applications utilize continuum models, which are calibrated based on volume‐averaging multi‐Gaussian geostatistical models, or utilizing smoothing regularization [ Brauchler et al ., ].…”

“…Together with the use of data sets obtained from spatially distributed field measurements, well-constrained flow and transport models can be derived. tomography in fractured rock, with successful applications to synthetic models [Hao et al, 2008;Ni and Yeh, 2008;Zha et al, 2016], laboratory [Sharmeen et al, 2012], and field cases [Meier et al, 2001;Vesselinov et al, 2001aVesselinov et al, , 2001bFranssen and G omez-Hern andez, 2002;Brauchler et al, 2003;Ni and Yeh, 2008;Illman et al, 2009;Castagna et al, 2011;Zha et al, 2015Zha et al, , 2016. All these applications utilize continuum models, which are calibrated based on volume-averaging multi-Gaussian geostatistical models, or utilizing smoothing regularization [Brauchler et al, 2003].…”

Mapping fracture flow paths with a nanoscale zero-valent iron tracer test and a flowmeter test

“…The hydraulic tomography approach can be used to indirectly infer the fracture connectivity (Hao et al 2008;Sharmeen et al 2012;Zha et al 2014Zha et al , 2015Zha et al , 2016; however, spatial resolution of the inferred tomograms is controlled by the observation interval. Thermal tracer tests have been conducted to delineate fracture flow paths between boreholes (Ma et al 2012;Read et al 2013;Klepikova et al 2014).…”