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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 14 (1930)

Issue: 8. (August)

First Page: 1059

Last Page: 1063

Title: Example of Deflecting Diamond-Drill Holes

Author(s): Robert Davis Longyear (2)


On a property on the Marquette Iron Range, Michigan, the iron formation overlying the ore was so much fractured that exploration had to be undertaken by means of angle holes from either side in more solid ground. All of the holes showed considerable curvature, one of them curving so much it was actually rising when completed. The curvature was initiated by increasing the pressure on the bit at the desired depth. Two of the holes were deflected at a considerable distance above the bottom, in order to explore new ground at depth without re-drilling the entire hole.

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