Application of well-logging methods to shot holes
<p>Electrical exploration, or the “well-logging,” of drill holes, for the oil industry, is a recent geophysical technique, dating only from 1928. There is no need to emphasize the absolute necessity of gathering reliable and complete information of all the formations encountered in the course...
| Summary: | <p>Electrical exploration, or the “well-logging,” of drill holes, for the oil industry, is a recent geophysical technique, dating only from 1928. There is no need to emphasize the absolute necessity of gathering reliable and complete information of all the formations encountered in the course of drilling. The oil industry has witnessed a continuous improvement in the manner of securing subsurface information. Drilling-speed charts, driller’s logs based on examination of cuttings, mechanical coring, paleontological analysis, wire-coring, etc., each furnishes some valuable data. But there is a constant urge to develop new means of investigation for the purpose of reducing the cost of drilling and obtaining more complete and reliable data. Today, electrical measurements constitute a new step forward, towards achieving this end.</p>
<p>The purpose of the work done by this author is to apply well-logging methods to the shot holes that are drilled by seismograph crews. In seismic prospecting it is necessary that the depth, below the surface, of the bottom of the low velocity or “weathered” layer be known accurately. By the methods now in use, this depth is calculated from the velocity of the seismic waves traveling through the weathered layer. However, by logging shot holes, one should be able to determine the thickness of the low velocity layer with a high degree of accuracy.</p>
<p>Another problem is seismic prospecting is the location of the top of the water table. At the present time this is done by noting the level at which the water stands in water wells. If no water wells are present one must simply guess at about the level of the top of the water table. By logging shot holes, it would seem probable that one should be able to locate the top of the water table accurately.</p>
<p>Thus by applying well-logging methods to shot holes, the author intends to locate the top of the water table, and, of greater importance, to locate the bottom of the weathered layer.</p>
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