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Interpretation of oscillatory water levels in observation wells during aquifer tests in fractured rock

Water Resources Research

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ORCID iD
https://doi.org/10.1029/WR025i010p02129

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Abstract

Oscillatory water levels in observation wells have commonly been recorded at the beginning of aquifer tests in highly transmissive fractured formations. In this paper, oscillatory water levels are predicted by the equations coupling the fluid movement in the observation well and the fluid movement in the surrounding formation. The equivalent-porous medium and dual-porosity models of fractured rock are two models considered in this analysis; however, other conceptual models of fractured media can also be coupled with the model presented here for fluid movement in the observation well. Type curves for the response of water levels in observation wells due to pumping in another well are generated by numerical inversion of the Laplace transform solution to the governing equations. Overdamped conditions, where inertial effects are insignificant, and underdamped conditions, where oscillations arise, are predicted by the solution to the governing equations. By matching water level measurements with the appropriate type curve, a conceptual model of the formation can be identified, and aquifer properties can be estimated. This analysis is applied in the interpretation of an aquifer test conducted in a fractured dolomite in northeastern Illinois. If the early time oscillations are ignored, the measured water levels can be explained by an equivalent-porous medium model. By analyzing the early time oscillations, however, the formation is shown to respond as a dual-porosity medium with a storativity of the fracture porosity that is an order of magnitude smaller than the storativity estimated from the equivalent-porous medium model.

Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Interpretation of oscillatory water levels in observation wells during aquifer tests in fractured rock
Series title:
Water Resources Research
DOI:
10.1029/WR025i010p02129
Volume:
25
Issue:
10
Year Published:
1989
Language:
English
Publisher:
American Geophysical Union
Description:
9 p.
First page:
2129
Last page:
2137