. Deep borehole surveys and problems. Boring. 202 DEEP BOREHOLE SURVEYS AND PROBLEMS Anderson's sand-line method a set of expansible steel-spring guides is run both above and below the instrument in its shell to prevent rotation in azimuth. A practically frictionless swivel connection is made from the end of the sand line to the instrument container. Readings are taken at each stand length and the station distances measured on the drill lengths, the operator taking the instrument as delivered from the well and interpreting. Fig. 142.—Plan of very deep borehole surveyed by Anderson. the results
. Deep borehole surveys and problems. Boring. 202 DEEP BOREHOLE SURVEYS AND PROBLEMS Anderson's sand-line method a set of expansible steel-spring guides is run both above and below the instrument in its shell to prevent rotation in azimuth. A practically frictionless swivel connection is made from the end of the sand line to the instrument container. Readings are taken at each stand length and the station distances measured on the drill lengths, the operator taking the instrument as delivered from the well and interpreting. Fig. 142.—Plan of very deep borehole surveyed by Anderson. the results on a special orientating stand (Fig. 141). Orientation is thus measured mechanically the direction of drift being referred to a north-south line on the derrick floor so that at each exposure the directional deflection is known at the surface. Interpretations will average within about 7 ft. of arc of being correct for vertical angles and 30 ft. for azimuth. The instrument is also self-checking in that all recorded points must fall on a curve when plotted. Various surveys. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Haddock, M. H. (Marshall Henry). New York, McGraw-Hill
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