Correlating hydrogeostratification with geostratification from nuclear logging and geoelectric sounding in water impregnated traps

Subsurface boundary conditions obtained through nuclear logging and geoelectric sounding were compared with the driller's log recorded in a number of boreholes drilled by employing modern down-the-hole hammer rig, to diagnose the relative merits of the methods and to portray the actual subsurface stratigraphic succession as well as hydrophysical conditions in saturated trap formations. It was observed that nuclear logging and resistivity sounding do not furnish the actual geostratigraphy due to lack of sufficient contrast in the relevant physical properties between successive lava flows, but reflects on the prevailing hydrostratigraphy. However, the informations thrown up by them are of immense technical value in guiding ground water development programme through sinking of wells in trappean terrians. It is shown that the horizontal correlation value of nuclear logging can be augmented by combining it with geoelectric sounding. This aids in enhancing the practical utility of nuclear logs in geohydrologic investigations. (author)