A record of the quality of a gravel pack and the quantity of solid particles it contains. The traditional logging technique uses a type of nuclear fluid densimeter, with a gamma ray source and a single detector. The number of gamma rays reaching the detector is inversely proportional to the gravel-pack density. The count rate is used qualitatively, being scaled in each well between zones with 100% pack and zero pack, or else compared before and after a repair to the pack.

The density measurement is not entirely independent of the formation, and is not effective when the density of the particles and the completion fluid are similar. In these cases, a neutron activation or neutron-porosity measurement may be used. Other techniques include a neutron porosity log and tracer measurements. Radioactive tracers may be coated on the outside of the particles or else included within the particles. They can be detected by gamma ray logs, or if a variety of tracers is used they can be tracked with a multiple-isotope log.