Identifying hydraulically conductive fractures with a slow-velocity borehole flowmeter

Canadian Geotechnical Journal
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Abstract

The U.S. Geological Survey used a recently developed heat-pulse flowmeter to measure very slow borehole axial water velocities in granitic rock at a site near Lac du Bonnet, Manitoba, Canada. The flowmeter was used with other geophysical measurements to locate and identify hydraulically conducting fractures contributing to the very slow vertical water flow in the two boreholes selected for study. The heat-pulse flowmeter has no moving parts and operates on the tag–trace principle. It is an improved version of the flowmeter developed by the Water Research Centre in England in 1975. The U.S. Geological Survey's heat-pulse flowmeter has a flow-measuring range in water of 0.06–6 m/min, and can resolve velocity differences as slow as 0.01 m/min. This is an order of magnitude slower than the stall speed of spinner flowmeters. The flowmeter is 1.16 m long and 44 mm in diameter. It was calibrated in columns of 76 and 152 mm diameter, to correspond to the boreholes studied. The heat-pulse flowmeter system is evaluated, and problems peculiar to the measurement of very slow axial water velocities in boreholes are discussed. Key words: flowmeter, borehole flow, low flow, borehole geophysics.

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Publication type Article
Publication Subtype Journal Article
Title Identifying hydraulically conductive fractures with a slow-velocity borehole flowmeter
Series title Canadian Geotechnical Journal
DOI 10.1139/t86-008
Volume 23
Issue 1
Year Published 1986
Language English
Description 10 p.
First page 69
Last page 78
Country Canada
State Manitoba
Other Geospatial Lac du Bonnet
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