Table 3. Types, properties measured, and application of geophysical logs used in Oasis Valley, Nevada (modified from Keys, 1990) |
Table 3. Types, properties measured, and application of geophysical logs used in Oasis Valley, Nevada (modified from Keys, 1990) |
Type of log |
Properties measured |
Application |
| Caliper | Borehole diameter | Provides borehole corrections for other logs, lithology, fractures, and hole volume |
| Natural gamma | Gamma radiation from natural sources in formation | Assists in the identification of lithology and stratigraphic correlation; may be related to clay content |
| Dual induction, multi-electrode, resistivity (conductivity, resistivity, short- and long-normal resistivity, and lateral resistivity) | Apparent resistivities of formation at different distances from borehole | Assists in the identification of lithology and stratigraphic correlation of units; provides qualitative or relative data on water quality |
| Single-point resistance | Resistance of formation and fluids in borehole and adjacent formations | Assists in the identification of lithology |
| Spontaneous potential | Electric potential between fluids in borehole and adjacent formations | Defines lithology, clay and shale content, and formation water quality |
| Acoustic velocity | Compressional-wave velocity through fluids and formations | Helps determine saturated zones, water levels, and lithology; indicator of fractures; used to estimate primary porosity |
| Fluid (temperature, fluid resistivity, and specific conductance) | Temperature, resistivity, and specific conductance of borehole fluids | Quality of borehole fluid, flow in borehole, and geothermal gradients |
| Acoustic televiewer | Acoustic reflectivity of borehole wall | Lithology determination; fracture location, width, orientation and character, strike and dip of beds. Additional processing provides deviation from the vertical of the borehole |
| Heat-pulse flowmeter | Vertical flow within the borehole | In-hole flow from fractures; apparent hydraulic conductivity of permeable zones |
