1. n. []

A record of the quantity of different radioactive isotopes near the borehole. The technique used is the same as for natural gamma ray spectroscopy, but measures the quantities of various short half-life radioactive tracers in addition to natural gamma rays. The log is run to monitor the results of processes that can be tagged, for example, hydraulic fracturing, gravel-pack placement, squeeze cementing, acid treatment and lost-circulation detection. Different radioactive tracers are added at different stages of the process so that by measuring the different tracers, it is possible to track the development, for example, of the fracture. The most common radioactive tracers are ¹¹⁰Ag (silver), ¹⁹⁵Au (gold), ¹³⁵I (iodine), ¹⁹²Ir (iridium), ¹²⁴Sb (antimony), and ⁴⁶Sc (scandium).

See related terms: gravel pack,  hydraulic fracturing,  lost circulation,  multiple-isotope spectroscopy,  squeeze cementing