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Summary
The following article deals with methods recently developed for a better utilization of information obtainable by diamond drilling.
Special attention is paid to the surveying of diamond drill holes in magnetic rocks and/or steel-casing. A short description is given of the Craelius method which can be used in drill holes of diameters from 36 mm ∅, equal to EX, up to 146 mm ∅, equal to 5.3/4″, and upwards to depths from the shallowest down to 1,000 meters, equal to 3,300 ft. The standard instrument is made for accurate measuring of inclined holes between 5° from the horizontal to the vertical. For measuring in horizontal holes, i. e., deviations off the horizontal, only a small alteration of the standard instrument is needed. Still another version of the instrument is used for measuring between 0° and 5° off the vertical if highly accurate determination of small deviations is needed. Some examples and a statistical study of the deviation of drill holes are included.
A new tool for intentional deviation of diamond drill holes is presented. This tool employs a very short “whipstock” which is affixed in a new manner.
A description is also given of the new Craelius core orientator which can be used for orientation of diamond drill cores. This new tool is placed in the core tube and remains there during the drilling. When the core tube is filled, hoisted and taken apart, the core orientator shows the position in which the core was, when the coring began. The Craclius core orientator can be used in core tubes from 36 mm ∅, (EX) and upwards. A subsequent survey of the drill hole enables the dip and strike of the formation penetrated to be determined.