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Altering Dissolved Oxygen to Determine Flow Conditions in Fractured Bedrock Wells

Authors

  • by Dariusz W. Chlebica,

  • Gary A. Robbins


  • Dariusz W. Chlebica, corresponding author, conducted this study as part of the requirements for his M.S. degree in the Center for Integrative Geosciences at the University of Connecticut, 354 Mansfield Road U-1045, Storrs, CT 06269–4087. He holds a B.S. degree in Chemistry and Geography from Worcester State College. He can be reached at Geosyntec Consultants Inc., 289 Great Road, Acton, Massachusetts 01720; dchlebica@geosyntec.com

  • Gary A. Robbins is a Professor of Geology in the Department of Natural Resources and the Environment at the University of Connecticut, 1376 Storrs Road, Storrs, CT 06269–4087. (860) 486–2448; fax (860) 486–5408; gary.robbins@uconn.edu. He holds a Ph.D. degree from Texas A& M University, a M.S. degree from Brown University, and a B.S. degree from Brooklyn College. He specializes in hydrogeology and education through simulation.

Abstract

A new approach to locate transmissive fractures and decipher vertical borehole flow conditions in fractured crystalline bedrock wells is presented, which uses dissolved oxygen (DO) as a benign tracer. The method was tested in two fractured crystalline bedrock wells previously characterized by televiewer and flow meter logging under both ambient and stressed (slug test) conditions. The method entailed elevating wellbore DO concentrations by circulating water through showerheads or injection of compressed air. The DO dilution was used to locate inflowing fractures. Changes in the DO concentration with time were used to ascertain flow within the borehole and to locate outflowing fractures and stagnant zones. Flow rates were also estimated. Fractures detected by the method corresponded to those observed by televiewer logging and for the most part were comparable to flow meter results. Given the effectiveness, time-efficiency and low cost, the method is a promising alternative to other methods currently in use to characterize transmissive fractures in wells.

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