Recent advances in portable borehole geophysical instrumentation and processing<br>software allow hydrogeologic characterization of sandstone aquifers. Lithostratigraphic<br>delineation is also performed. A slimline logging probe allows logging of 4 normal<br>resistivity measurements (8, 16, 32, and 64 inch), as well as single point resistance,<br>spontaneous potential, natural gamma, fluid temperature and fluid resistivity. The data<br>can be quickly and easily processed on site to provide derived parameters and properties.<br>Hydrogeologic information can be easily calculated using processing software. Water<br>resistivity is indicated using shallow and deep resistivity measurements along with the<br>resistivity of the mud filtrate. Total dissolved solids can be found fi-om the water<br>resistivity. Porosity can be determined from Archie’s Law if a fresh water correction is<br>used. Hydraulic conductivity is indicated using depth of mud filtrate invasion. Examples<br>illustrate that calculated parameters agree with measured or otherwise indicated values.<br>Lithostratigraphic units can be delineated by synthesizing an approximated Laterolog7 log.<br>The synthesized focusing currents provide good a indication of bed boundaries. The<br>models generated from data sets obtained with the new multi-spaced normal resistivity<br>probe provides better vertical resolution due to the 8 inch normal resistivity measurement.


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