Compensated Neutron instrument works with an Americium Beryllium source and two detectors. The source emits high-energy neutrons, which undergo scattering in the formation, lose energy and produce gamma rays. The thermal neutrons are measured by the two detectors in the tool. The tool can be run in both open and cased holes and in most types of mud. In order to minimize the borehole effects, the tool is run decentralized.
The neutron count rates of the two detectors are related to the amount of hydrogen in the formation. Since most of the hydrogen atoms are present in fluids, the number of detected neutrons provide a measurement for calculating porosity of the formation. The Neutron tool is normally run in combination with the Density tool.
Some typical applications are :