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Book Chapter

Evaluation of a discrete-depth heat dissipation test for thermal characterization of the subsurface

By
Stephen M. Sellwood
Stephen M. Sellwood
Department of Geoscience, University of Wisconsin–Madison, 1215 W. Dayton Street, Madison, Wisconsin 53706, USA
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Jean M. Bahr
Jean M. Bahr
Department of Geoscience, University of Wisconsin–Madison, 1215 W. Dayton Street, Madison, Wisconsin 53706, USA
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David J. Hart
David J. Hart
Wisconsin Geological and Natural History Survey, University of Wisconsin–Extension, 3817 Mineral Point Road, Madison, Wisconsin 53705, USA
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Published:
March 01, 2016

Heat transfer in the subsurface can vary with depth due to variations in the thermal conductivity of the geologic medium as well as variations in groundwater flow velocity. However, traditional thermal response tests (TRTs) do not allow for evaluation of the depth variability of heat transfer. We investigate the potential for using discrete-depth heat dissipation tests in open, water-filled boreholes to evaluate variations in heat exchange rate with depth. Heat dissipation tests were initiated at target depths in a test well using an electrical resistance heater. Heat dissipation was monitored by measuring borehole water temperature through time using a fiber-optic distributed temperature sensing system. Temperature data were used to compare the thermal response at different depths in the borehole. To account for both the thermal conductivity of the geologic medium and the groundwater flow velocity, we used a numerical groundwater flow model (MODFLOW) and solute transport model (MT3DMS) to simulate heat dissipation tests. Simulation results indicate the measured response to a heat dissipation test in an open borehole is strongly dependent on the measurement location within the borehole; thus, data are ambiguous when the measurement location is uncontrolled. However, modeling results also indicate that the thermal response of a heat dissipation test as measured at the center of the borehole is sensitive to variations in thermal conductivity and groundwater flow velocity, suggesting that heat dissipation tests are a potentially useful method for characterizing depth variability in thermal properties if a centralized temperature measurement method is used to monitor the tests.

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GSA Special Papers

Geothermal Energy: An Important Resource

Gordon R. Osinski
Gordon R. Osinski
Centre for Planetary Science and Exploration, Departments of Earth Sciences and Physics and Astronomy, University of Western Ontario, 1151 Richmond St., London, ON N6A 3K7, Canada
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David A. Kring
David A. Kring
Center for Lunar Science and Exploration, Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, Texas 77058, USA, and National Aeronautics and Space Administration (NASA) Lunar Science Institute, and NASA Solar System Exploration Research Virtual Institute
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Geological Society of America
Volume
519
ISBN print:
9780813725192
Publication date:
March 01, 2016

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