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A common gamma-ray log records the total radiation and cannot distinguish between the radioactive elements, while a spectral gamma ray log (see below) can. For standard gamma-ray logs, the measured value of gamma-ray radiation is calculated from concentration of uranium in ppm, thorium in ppm, and potassium in weight percent: e.g., GR API = 8 ...
The formation evaluation gamma ray log is a record of the variation with depth of the natural radioactivity of earth materials in a wellbore. Measurement of natural emission of gamma rays in oil and gas wells are useful because shales and sandstones typically have different gamma ray levels.
This bombards the formation with high energy gamma rays. The attenuation of these gamma rays gives an accurate measure of formation density; this has been a standard oilfield tool since 1965. Another source is americium berylium (Am-Be) neutron source used in evaluation of the porosity of the formation, and this has been used since 1950. In a ...
The gamma ray log is useful in holes drilled with air or with oil based muds, as these wells have no SP voltage. Even in water-based muds, the gamma ray and SP logs are often run together. They comprise a check on each other and can indicate unusual shale sections which may either not be radioactive, or may have an abnormal ionic chemistry.
In 2004 H.E.S.S. was the first IACT experiment to spatially resolve a source of cosmic gamma rays. In 2005, it was announced that H.E.S.S. had detected eight new high-energy gamma ray sources, doubling the known number of such sources. As of 2014, more than 90 sources of teraelectronvolt gamma rays were discovered by H.E.S.S. [2]
In 1950, Leonidas D. Marinelli developed and applied a low-level gamma-ray whole body counter to measure people who had been injected with radium in the early 1920s and 1930s, contaminated by exposure to atomic explosions, and by accidental exposures in industry and medicine [4] [5] The sensitive methods of dosimetry and spectrometry Marinelli ...
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The first gamma ray source to be discovered was the radioactive decay process called gamma decay. In this type of decay, an excited nucleus emits a gamma ray almost immediately upon formation. [note 1] Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, while studying radiation emitted from radium.