1. n. [Production Logging]
A record of the density in and around a completed well using a radioactive source of gamma rays and a detector. The log is recorded with a nuclear fluid densimeter. Originally, photon logs were run to determine the size of salt caverns. More recently, they have been run to evaluate the quality of gravel packs and sand cavities, and are then synonymous with gravel-pack logs.
Synonyms: gravel-pack log
