Resistivity Well Logging Natural Gamma Well Logger Sp Logging Tool Geologger Geophysical Logging Tools Gamma Ray Logging Well Logger Borehole Logging System
It can provide a wealth of information that is critical in gaining a better understanding of subsurface conditions needed for ground-water and environmental studies. Geophysical logs provide unbiased continuous and in-situ data and generally sample a larger volume than drilling samples.
Caliper logs record borehole diameter. Changes in borehole diameter are related to well construction, such as casing or drilling-bit size, and to fracturing or caving along the borehole wall. Because borehole diameter commonly affects log response, the caliper log is useful in the analysis of other geophysical logs, including interpretation of flowmeter logs.
Gamma logs record the amount of natural gamma radiation emitted by the rocks surrounding the borehole. The most significant naturally occurring sources of gamma radiation are potassium-40 and daughter products of the uranium- and thorium-decay series. Clay- and shale-bearing rocks commonly emit relatively high gamma radiation because they include weathering products of potassium feldspar and mica and tend to concentrate uranium and thorium by ion absorption and exchange.
Single-point resistance logs record the electrical resistance from points within the borehole to an electrical ground at land surface. In general, resistance increases with increasing grain size and decreases with increasing borehole diameter, fracture density, and dissolved-solids concentration of the water. Single-point resistance logs are useful in the determination of lithology, water quality, and location of fracture zones.
Spontaneous-potential logs record potentials or voltages developed between the borehole fluid and the surrounding rock and fluids. Spontaneous-potential logs can be used in the determination of lithology and water quality. Collection of spontaneous-potential logs is limited to water- or mud-filled open holes.
Normal-resistivity logs record the electrical resistivity of the borehole environment and surrounding rocks and water as measured by variably spaced potential electrodes on the logging probe. Typical spacing for potential electrodes are 16 inches for short-normal resistivity and 64 inches for long-normal resistivity. Normal-resistivity logs are affected by bed thickness, borehole diameter, and borehole fluid and can only be collected in water- or mud-filled open holes.
Electromagnetic-induction logs record the electrical conductivity or resistivity of the rocks and water surrounding the borehole. Electrical conductivity and resistivity are affected by the porosity, permeability, and clay content of the rocks and by the dissolved-solids concentration of the water within the rocks. The electromagnetic-induction probe is designed to maximize vertical resolution and depth of investigation and to minimize the effects of the borehole fluid.
Fluid-resistivity logs record the electric resistivity of water in the borehole. Changes in fluid resistivity reflect differences in dissolved-solids concentration of water. Fluid-resistivity logs are useful for delineating water-bearing zones and identifying vertical flow in the borehole.
Temperature logs record the water temperature in the borehole. Temperature logs are useful for delineating water-bearing zones and identifying vertical flow in the borehole between zones of differing hydraulic head penetrated by wells. Borehole flow between zones is indicated by temperature gradients that are less than the regional geothermal gradient, which is about 1 degree Fahrenheit per 100 feet of depth.
Flowmeter logs record the direction and rate of vertical flow in the borehole. Borehole-flow rates can be calculated from downhole-velocity measurements and borehole diameter recorded by the caliper log. Flowmeter logs can be collected under non-pumping and(or) pumping conditions. Impeller flowmeters are the most widely used but they generally cannot resolve velocities of less than 5 ft/min. Heat-pulse and electromagnetic flowmeters can resolve velocities of less than 0.1 ft/min.
Television logs record a color optical image of the borehole. In addition to being recorded on video-cassette-recorder tape, the optical image can be viewed in real time on a television monitor. Well construction, lithology and fractures, water level, cascading water from above the water level, and changes in borehole water quality (chemical precipitates, suspended particles, and gas) can be viewed directly with the camera.
Acoustic-televiewer logs record a magnetically oriented, photographic image of the acoustic reflectivity of the borehole wall. Televiewer logs indicate the location and strike and dip of fractures and lithologic contacts. Collection of televiewer logs is limited to water- or mud-filled open holes.
| No. |
Probe name |
Usage |
| 1 |
M552 Combined sidewall probe |
Density (DsCD), Natural Gamma, Resistivity, Caliper and spontaneous potential |
| 2 |
M451 Combined density probe |
Density (DsCD), Natural Gamma, Three direction laterolog and spontaneous potential |
| 3 |
S524-1S Acoustic wave probe |
SP, sound velocity, acoustic amplitude |
| 4 |
CZ521- Combined Natural Gamma probe |
Magnetic locator, natural gamma |
| 5 |
W422Temperature and liquid resistivity combined probe |
Well temperature, liquid resistivity |
| 6 |
CX3019 SP, inclination, natural gamma combined probe |
SP, inclination, natural gamma |
| 7 |
JSC-1 Digital inclination probe |
Inclination |
| 8 |
S524 Acoustic wave probe |
Acoustic wave |
| 9 |
H411 Magnetic susceptibility probe |
Seeking for magnetic iron ores |
| 10 |
X411 Three-lateral direction resistivity laterolog probe |
Determines the resistivity of rock strata. |
| 11 |
J411 Caliper probe |
check the integrity of well and provide additional information to help |
| 12 |
LLY-1Flow probe |
Liquid flow |
| 13 |
R411 Natural gamma probe |
Nature gamma |
| 14 |
JD-1Conventional resistivity log probe |
SP, NR, and LR |
| 15 |
JD-3 Soft-elctrode probe |
SP, NR, and IP |
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