Idaho Water Science Center

USGS INL Project Office

Working in cooperation with the U.S. Department of Energy and the
Idaho National Laboratory

Geophysical Logging

Geophysical logging van in action. Click to view larger image in a new window.

Rocks, sediments and fluids in the subsurface of the Earth have different physical and chemical properties that can be detected in boreholes by physical, radiogenic and electromagnetic methods. These physical and chemical properties are used to determine lithology, bed thickness, and structures in the subsurface.

Geophysical logging is the use of physical, radiogenic or electromagnetic instruments lowered into a borehole to gather information about the borehole, and about the physical and chemical properties of rock, sediment, and fluids in and near the borehole. The USGS INL Project Office provides video, physical and geophysical logging services for wells on the INL. We use the data gathered by these methods and by water sampling to study ground water, ground water movement, and subsurface geology on the INL and in the Snake River Plain aquifer.

Geophysical profile of USGS 128, p. 1. Click to view larger image in a new window.USGS INL Project Office hosts The Idaho National Laboratory (INL) Geophysical Logging archive, a web-based data repository for borehole geophysical logs. Selected geophysical log files include neutron, gamma-gamma, natural gamma, borehole deviation, caliper, and fluid temperature.

The USGS also maintains an extensive archive of INL-related geophysical logs consisting of LOG (binary) and LAS (ASCII) processed files. Researchers may obtain this data by contacting Amy Wehnke, (208)526-2060, ajwehnke@usgs.gov

 

 

Video icon Video Logging is done by lowering a video camera down-hole, producing a video tape or DVD of the interior of a borehole-very useful for seeing fractures and "washouts," areas where sediment has fallen away from the borehole, leaving a cavity.
Nuclear particle animation Neutron logging uses a neutron source and a detector in a probe to measure the hydrogen content of surrounding media. In the unsaturated zone, above the water table, neutron logging measures moisture content. Below the water table, neutron logging measures total porosity. Neutron logging provides data under a variety of conditions in cased and uncased boreholes.
Instrument animation. Gamma-Gamma logging uses an instrument with a gamma radiation source and one or more detectors to measure the bulk density of surrounding rocks or sediment.
Nuclear particle animation. Natural-gamma logs record total gamma radiation in boreholes. Gamma radiation occurs naturally by radioactive decay of potassium-40 and the uranium-thorium isotope series, and by contamination by human activity. Fine-grained detrital sediments preferentially take up gamma-emitting isotopes; most basalts do not contain large amounts of naturally occurring gamma-emitting isotopes, and crystalline rock, such as basalt, is less likely to preferentially absorb gamma emitters. Natural gamma logs are a useful tool to help define sedimentary interbeds in the subsurface of the Snake River plain.
Deviation animation. Deviation records the amount and direction a borehole deviates from vertical. As with caliper measurements, amount and direction of deviation must be considered when analyzing logs because many techniques are distance-dependent.
Conductivity animation. Fluid Conductivity logs record the ability of fluid in a borehole to transmit electricity. The electrical conductance of a fluid depends on the chemical composition and amount of dissolved solids in the fluid.
Caliper animation. Caliper Logging-a caliper is an instrument with spring-loaded "fingers" that touch the sides of the borehole as it is moved up the hole, transmitting a record of the cross-sectional shape of the hole. Many geophysical methods are affected by distance; caliper logging is necessary so that measurements can be adjusted for changes in hole diameter.
Fluid flow animation. Fluid-flow meter logging records direction and speed of fluid flow in a borehole.

Temperature animation.

 Temperature logging records water temperature. Because water gains and loses heat more slowly than rocks, sediment, and air, temperature profiles can be used to study rates and direction of ground water movement.

References for this page:

Go to http://ny.water.usgs.gov/projects/bgag/intro.text.html for a concise introduction to geophysical logging applications in hydrology.

Animations were created by John H. Williams, U.S. Geological Survey. 425 Jordan Road, Troy, New York 12180.

Keys, Scott, MacCary, L. M., 1971 Application of Borehole Geophysics to Water-Resources Investigations, Techniques of Water-Resources Investigations Book 2, Chapter E1, http://pubs.er.usgs.gov/usgspubs/twri/twri02E1

Keys, W. S., 1990, Techniques of Water-Resources Investigations, Book 2, Chapter E-2, U. S. Geological Survey, http://pubs.er.usgs.gov/usgspubs/twri/twri02E2

Stevens, H. H. Jr., Ficke, J. F., and Smoot, G. F., 1976, Techniques of Water-Resources Investigations Book 1, Chapter D1, Water Temperature—Influential Factors, Field Measurement, and Data Presentation, U.S. Geological Survey, http://pubs.er.usgs.gov/usgspubs/twri/twri01D1