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Hydraulic single-borehole techniques for characterizing hydraulic conductivity in highly permeable aquifers: Slug test, borehole flowmeter test, and dipole -flow test
Three single-borehole hydraulic techniques for estimation of hydraulic conductivity, the dipole-flow test, the slug test, and the borehole flowmeter test were applied in two highly permeable aquifers. Modified procedures for the analysis of the data from each technique are proposed. ^ The steady-state dipole flow test (DFT) was used to characterize the statistics of horizontal hydraulic conductivity (Kr) of a highly permeable, heterogeneous, and thin aquifer. A new “by-chamber” interpretation is proposed that is based on drawdown within each individual chamber. This interpretation yields detailed information on the structure of heterogeneity of the aquifer. Descriptive statistics from the DFT compare well with those from previous field and laboratory tests. The role of confining boundaries in the DFT interpretation is shown to be negligible even in this case of a very thin (<4 m>thick) and highly permeable (49 to 6000 m/day) aquifer. ^ Existing models for slug-test responses in highly permeable formations do not address the indirect measurement of water level recovery by a transducer positioned at depth in the water column. Given the rapid and often oscillatory nature of test responses, the traditional hydrostatic relationship between the water level and the transducer-measured head in the water column may not be appropriate. A general dynamic interpretation is proposed that transforms model generated water-level responses to transducer readings. Failure to use this approach can lead to a significant underestimation of Kr. ^ Recent numerical studies have shown that head loss across the electromagnetic borehole flowmeter (EBF) during the borehole flowmeter test (BFT) redistributes drawdown near the pumping well and discharge to the well, which may lead to considerable errors in estimates of layer hydraulic conductivity Kr,i . A hydraulic interpretation of the EBF test is developed, which considers this head loss. It is based on the derived analytical solutions for head distribution in the vicinity of the pumping well for the case of a confined homogeneous aquifer. The hydraulic approach is applied to an existing profile of apparent Kr,i′, estimated from the conventional interpretation, to resolve it to the true aquifer Kr,i. However, application to a field data set revealed that the constraint of aquifer homogeneity limits the applicability of the hydraulic approach. ^
Zurbuchen, Brian Roy, "Hydraulic single-borehole techniques for characterizing hydraulic conductivity in highly permeable aquifers: Slug test, borehole flowmeter test, and dipole -flow test" (2000). ETD collection for University of Nebraska - Lincoln. AAI9992018.