Scale Dependency of Hydraulic Conductivity Measurements

The hydraulic conductivity of five stratigraphic units in a carbonate aquifer has been measured with slug, pressure, and pumping tests, and with two calibrated digital models. The effective test radii range from less than one to greater than 10,000 meters. On log-log plots hydraulic conductivity increases approximately linearly with test radius to a range between 20 and 220 meters, but thereafter, it is constant with scale. The increase in magnitude of hydraulic conductivity is similar to scaling effects reported at seven additional sites in a variety of geologic media. Moreover, the increase in magnitude correlates with an increase in variance of log-hydraulic conductivity measured at successively greater separation distances. The rate of increase in both parameters, and particularly the range, have characteristic values for different pore systems. The larger ranges are consistently present in units with greater secondary porosity. Therefore, scaling effects provide a qualitative measure of the relative importance of secondary and primary permeability, and they can potentially be used to distinguish the dominant type of pore system.

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