| Abstract: | Various conventional geophysical borehole measurements were made in conjunction with measurements using a recently designed, low-frequency, acoustic-waveform probe and slow velocity flowmeter for characterization of a fractured mafic intrusion in southern Ontario, Canada. Conventional geophysical measurements included temperature, caliper, gamma, acoustic, single-point resistance, and acoustic televiewer logs. Hole stability problems prevented the use of neutron and gamma-gamma logs, because these logs require that a radioactive source be lowered into the borehole. Measurements were made in three boreholes as much as 850 m deep and penetrating a few tens of meters into granitic basement. All rocks within the mafic intrusion were characterized by minimal gamma radiation and acoustic velocities of about 6.9 km/sec. The uniformity of the acoustic velocities and the character of acoustic-waveform logs made with a conventional high-frequency logging source correlated with the density of fractures evident on televiewer logs. Sample intervals of high-frequency waveform logs were transformed into interpretations of effective fracture opening using a recent model for acoustic attenuation in fractured rocks. The new low-frequency sparker source did not perform as expected at depths below 250 m because of previously unsuspected problems with source firing under large hydrostatic heads. A new heat-pulse, slow velocity flowmeter was used to delineate in detail the flow regime indicated in a general way by temperature logs. The flowmeter measurements indicated that water was entering 2 of the boreholes at numerous fractures above a depth of 200 m, with flow in at least 2 of the boreholes exiting through large isolated fractures below a depth of 400 m. (Author ‘s abstract) |
| Genre: | USGS Numbered Series |
| ProdID: | 29000 |
| Citation Author: | Paillet, F. L.; Hess, A. E. |
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| Citation Language: | ENGLISH |
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| Citation Phsyical Description: | vi, 37 p. :ill., maps ;28 cm. |
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| Citation Publisher: | U.S. Geological Survey, |
| Citation Series: | Water-Resources Investigations Report |
| Citation Series Code: | WRI |
| Citation Series Number: | 86-4052 |
| Citation Search Results Text: | Geophysical well-log analysis of fractured crystalline rocks at East Bull Lake, Ontario, Canada; 1986; WRI; 86-4052; Paillet, F. L.; Hess, A. E. |
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| Citation Year: | 1986 |
| Type: | citation/reference |
| Text: | Geophysical well-log analysis of fractured crystalline rocks at East Bull Lake, Ontario, Canada; 1986; WRI; 86-4052; Paillet, F. L.; Hess, A. E. |
| URL (THUMBNAIL): | http://pubs.usgs.gov/wri/1986/4052/report-thumb.jpg |
| URL (DOCUMENT): | http://pubs.usgs.gov/wri/1986/4052/report.pdf |
| Date Other: | Sat, 1 Jan 1994 00:00 -0600 |
| Publisher: | U.S. Geological Survey, |
