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Publications > Williams and others, 2010.

Cross-borehole flow analysis to characterize hydraulic connections in fractured granite, Bohemian-Moravian Highland, Czech Republic

J.H. Williams
U. S. Geological Survey, 425 Jordan Road, Troy, NY 12180, jhwillia@usgs.gov

F.L. Paillet
U.S. Geological Survey (Emeritus), 11 Sherman Place, Unit 5015, Storrs, CT 06269, Storrs-Mansfield, CT 06269

J. Urik
Charles University, Albertov 6, Prague, 128 43, Czech Republic

J. Lukes
Aquatest a. s, Geologicka 4, Prague, 152 00, Czech Republic

M. Kobr
Charles University, Albertov 6, Prague, 128 43, Czech Republic

Abstract

Cross-borehole flow analysis was used to characterize the hydraulic connections between two boreholes completed in fractured granite in the Bohemian-Moravian Highland of the Czech Republic. Cross-borehole flow analysis is designed to determine the hydraulic characteristics of fracture connections between boreholes rather than those of discrete fractures that intersect a single borehole. The two boreholes, which were 200 meters deep and spaced 20 meters apart, were initially characterized through collection and analysis of a standard suite of geophysical logs and application of the borehole dilution method under ambient and pumped conditions. The cross-borehole flow test was conducted by measuring transient flow with a high-resolution flowmeter at depth stations located between the transmissive fractures in one of the boreholes during short-term pumping and recovery cycles in the other borehole. Insight into the character of the fracture connections was gained through comparison of measured flows and flows simulated by use of a numerical model with adjustable connection geometry and hydraulic properties. The presence of a primary and two secondary hydraulic connections, and their relative transmissivity and storage, inferred from the cross-borehole flow analysis were corroborated by tracer testing. The results of the cross-borehole flow analysis demonstrated that it is possible to evaluate the characteristics of a fracture-flow network despite being restricted to making measurements in boreholes in which a local population of discrete fractures controls hydraulic communication with the larger-scale aquifer system.


Final copy as submitted to the Geological Society of America for publication as: Williams, J.H., Paillet, F.L., Urik, J., Kobr, M., and Mares, S., 2010, Cross-borehole flow analysis to characterize hydraulic connections in fractured granite, Bohemian-Moravian Highland, Czech Republic [abs.], in GSA Annual Meeting, 31 October-03 November 2010, Denver, Colorado, proceedings: Geological Society of America, Boulder, Colorado.

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