Application of Geophysical Logging to Groundwater Studies in Southeastern Saskatchewan

Abstract

Single-point resistance and spontaneous potential logs in fresh-water filled rotary-drilled test-holes provide data useful in geohydrologic studies in Saskatchewan. These geophysical logs are made by many of the water well drilling contractors in Saskatchewan on a routine basis. The logs provide good resolution of various lithologic units and provide data required to estimate the salinity of water in sand beds prior to constructing a well.Caliper logging offers a potentially useful method for evaluating hole conditions and the effect of drilling techniques on the formation in completion zones. The casing collar locator log run in a previously constructed well near Estevan demonstrates that this device can provide an accurate and objective measurement of the position and length of each joint of casing, the position of the screen assembly, and the location of screened and blanked intervals within the screen assembly. This tool should find general application in water well construction and maintenance practice.The neutron-epithermal neutron log provides a method of measuring the porosity of sand and gravel beds. The response of the gamma log is similar to that of the spontaneous potential log and the neutron-epithermal neutron log deflects in a fashion similar to the resistance and resistivity logs. Nuclear logs offer the advantage that they can be run in cased or uncased boreholes which may be filled with any type of fluid. They require more complicated and expensive instrumentation and slow-speed logging to obtain the required resolution. The normal resistivity logs offer the possibility of determining the concentration of dissolved solids in the formation water. The gamma-gamma log is a poor alternative to the natural gamma and neutron log for stratigraphic correlations.

Geotechnical applications of electrical borehole logging in southern Saskatchewan

“…Keyes (1968) described how this and other logging methods can be used for water well logging in groundwater hydrology. Dyck et al (1972) developed field procedures that are particularly well suited for geotechnical applications in southern Saskatchewan. The procedures and equipment in use today by both geologists and engineers are still essentially the same in principle as those described in this article.…”

“…The practice of delegating this important phase of the program to inexperienced technicians is to be avoided. A detailed description of the field procedures, which are used by geotechnical engineers in Saskatchewan, has been described by Dyck et al (1972).…”

“…The methodology involved is described by Dyck et al (1972) and Keyes (1968). Where the salinity of the formation water is greater than that of the mud, the SP curve moves to the left or the potential is negative with respect to the potential in the shale beds or confining layers.…”

“…But it does provide continuity in the sedimentary sequence penetrated by the borehole where core recovery could be incomplete. Dyck et al (1972) experimented with various types of geophysical well logging equipment in southern Saskatchewan. They tested radiation, mechanical, and electric logging devices mainly for groundwater exploration.…”