Oilfield Glossary
Oilfield Glossary
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Tools

gamma ray densitometer

1. n. [Production Logging]
A device for measuring the density of fluids in a completed well, using a radioactive source of gamma rays and a detector. In most instruments, a 137Cs (cesium) or 241Am (americium) source is used to induce Compton scattering, as in the openhole density measurement, except that the device is unfocused. The count rate at the detector then depends primarily on the density of the fluids in the well. In some devices, the fluids pass through an open space in the body of the tool within which the measurement is made. The results then reflect the density of the fluids passing through the tool. In other devices, the source and detector are isolated so that the gamma rays pass outside the tool. The results then reflect some average density of all the fluids within the well. In smaller casings, some formation signal may contaminate the measurement. Compared with a gradiomanometer, the nuclear fluid densimeter is a less direct measurement of density, and has a statistical uncertainty and less resolution. On the other hand, it is not affected by well deviation, friction or kinetic effects.