Frequency Dependent Hydraulic Properties Estimated from Oscillatory Pumping Tests in an Unconfined Aquifer

Tuesday, October 6, 2015: 10:00 AM
Avinoam Rabinovich1, Warren Barrash2,3, Michael A Cardiff4, David L Hochstetler5, Tania Bakhos5, Gedeon Dagan6 and Peter K Kitanidis2, (1)Stanford University, Energy Resources Engineering, Stanford, CA, United States, (2)Stanford, Civil and Environmental Engineering, Stanford, CA, United States, (3)Boise State University, Boise, ID, United States, (4)University of Wisconsin-Madison, Geoscience, Madison, WI, United States, (5)Stanford University, Stanford, CA, United States, (6)Tel Aviv University, Tel Aviv, Israel
Abstract:
Oscillatory pumping tests were conducted at the Boise Hydrological Research Site. A periodic pressure signal is generated by pumping and injecting water into the aquifer consecutively and the pressure response is recorded at many points around the source. We present and analyze the data from the field test after applying Fourier analysis. We then match the data with a recently derived analytical solution for homogeneous formations to estimate the equivalent aquifer properties: conductivity K, specific storage Ss and specific yield Sy. The estimated values are shown to be in agreement with previous estimates conducted at this site.

We observe variations in the estimated parameters with different oscillation periods of pumping. The trend of the parameters with changing period is discussed and compared to predictions by existing theory and laboratory experiments dealing with dynamic effective properties. It is shown that the results are qualitatively consistent with recent works on effective properties of formations of spatially variable properties in oscillatory flow. To grasp the impact of heterogeneity, a simple configuration is proposed, to help explain the observed increase in effective conductivity with decreasing period.

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