1. n. [Production Logging]

A technique for determining the velocity of fluid flow in an injection well based on measuring the time a slug of radioactive tracer takes to move down the well. The analysis is usually performed as part of a tracer-loss measurement. The depth of the slug is measured by running repeated gamma ray logs at well-defined time intervals. From the differences in depth and time, the velocity can be determined.

See: production log,  radioactive-tracer log,  tracer measurement,  velocity shot measurement