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USGS Groundwater Information: Branch of Geophysics

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Summary of Selected Borehole Geophysical Logging Methods

Table 1. Summary of selected geophysical logging methods
[Relative cost: 1–3 inexpensive to expensive; time: 1–3 fast to slow; relative difficulty: 1–3 easy to difficult]

Method Purpose Property measured Cost Time Difficulty
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

Modified from:

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.

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