Interpretation of single-well tracer tests using fractional-flow dimensions. Part 2: A case study |
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Authors: | Kornelius Riemann Gerrit van Tonder Panganai Dzanga |
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Institution: | (1) University of the Free State, Institute for Groundwater Studies, Box 339, Bloemfontein 9300, South Africa, |
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Abstract: | Generalized equations using fractional-flow dimensions were derived to estimate the Darcy and groundwater-flow velocities
obtained from the point-dilution and the single-well injection-withdrawal field tests. Flow velocities can only be estimated
from single-well tests if the kinematic porosity or the hydraulic conductivity and hydraulic gradient are known a priori.
A pumping test performed on the boreholes will yield an estimate of the fractional-flow dimension and the extent of the flow
region by applying the generalized radial flow (GRF) model of Barker Barker JA (1988) A generalized radial flow model for
hydraulic tests in fractured rock. Water Resour Res 24(10):1796–1804]. These parameters are used in the generalised equations
for the single-well tracer tests to estimate the flow-through area and, therewith, the Darcy or flow velocity.
The generalized procedure, described in detail in Part 1 of this paper, is applied to two boreholes on the Campus Test Site
located at the University of the Free State, Bloemfontein, South Africa, and it is shown that the two independent tests (i.e.
the point-dilution and the single-well injection-withdrawal tests) yield similar estimates of the natural-seepage velocity
in the aquifer. The estimated natural-flow velocity obtained by using fractional dimensions is about two times higher than
the velocity estimated by using the standard method (i.e. flow dimension n=2, flow thickness equal to length of the sealed-off section of the borehole).
Electronic Publication |
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Keywords: | Fractional-flow dimension Fractured aquifer Injection-withdrawal test Point-dilution test Tracer |
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