A Discussion of Deep Drilling tn the Blind River Area
More than 700,000 feet of diamond drilling was completed in the Blind River area between 1953 and 1958. Much of this drilling was at depths which are still not usual in North America. However, as the tendency is to deeper holes, factual data from the Blind River operation may weil provide information of value in future programs. Rates of drilling decreased with increasing depth, but uncommonly good rates (an average of over 50 feet per day over more than 4,000 feet of hole) were achieved with proper engineering and care. Costs varied as contractors and geologists became familiar with the area. Hole deviation in the Blind River area was locally severe and control of the hole trace became a major problem. Careful surveying was necessary and found to be highly reliable. It was found that control of the hole trace above 1,500 feet was much more difficult than at depths below 1,500 feet. This is explained by the mechanics of the drilling operation. Various methods of controlling hole deviation were attempted and, coupled with proper pre-engineering of the hole, were partially successful. It was concluded that deep diamond drill holes require continuons engineering care.
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