USGS Groundwater Information: Hydrogeophysics Branch
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Table 1. Summary of selected geophysical logging methods
[Relative cost: 13 inexpensive to expensive; time: 13 fast to slow; relative difficulty: 13 easy to difficult]
|Caliper||Generate continuous profile of borehole diameter||Borehole diameter||1||1||1|
|Single-point resistance||Delineate changes in lithology, porosity, and (or) clay content of surrounding formation or changes in porosity and total dissolved solids in the formation water||Resistance of formation, fluids in formation, and borehole fluids||1||1||1|
|Normal resistivity||Determine changes in resistivity of the fluids in the formation and (or) lithology||Resistivity of the formation; with additional data, true resistivity can be calculated||1||1||1|
|Electromagnetic Induction||Delineate changes in rock type or in electrical properties of fluids in the rock formation; corroborate surface resistivity surveys||Bulk apparent conductivity of the formation and pore fluids surrounding the borehole||1||2||2|
|Fluid resistivity||Identify differences in concentration of total dissolved solids in borehole fluid; these differences typically indicate sources of water that have come from different transmissive zones||Electrical resistivity of borehole fluid, from which specific conductance is calculated||1||1||1|
|Fluid temperature||Identify where water enters or exits the borehole||Temperature of borehole fluid; differential temperature (rate of change of the temperature) is calculated||1||1||1|
|Heat-pulse, electromagnetic, and spinner flowmeter||Map fluid flow regime and transmissive fractures in the borehole||Direction and magnitude of vertical flow within the borehole||3||3||3|
|Camera||Characterize rock type, identify changes in rock type and small-scale geologic structures, locate and describe fractures, describe borehole construction, and identify problems with borehole integrity and (or) possible signs of contamination||Visual fish-eye view and side-looking view of borehole||2||2||2|
|Acoustic televiewer||Map location and orientation of fractures intersecting borehole and generate a high-resolution acoustic-caliper log||Amplitude and travel time of the reflected acoustic signal||3||3||3|
|Deviation||Three-dimensional geometry of the borehole||Azimuthal direction and the inclination of the borehole||2||2||2|
Johnson, C.D., and Williams, J.H., 2003, Hydraulic logging methods - a summary and field demonstration in Conyers, Rockdale County, Georgia, in ed. Williams, L.J., Methods used to assess the occurrence and availability of ground water in fractured-crystalline bedrock - an excursion into areas of Lithonia Gneiss in eastern metropolitan Atlanta, Georgia: [Atlanta, Georgia], Georgia Geologic Survey, Guidebook 23, p. 40-47.