1. n. [Production Logging]

A technique in which a tracer is injected into the flow stream of a production or injection well to determine fluid paths and velocities. Radioactive tracers have been used from the 1940s and are still common for determining flow profiles in injection wells. Tracers with high neutron-capture cross section, such as borax or high-salinity water, were introduced in the 1970s to record injection/pulsed neutron logs. In multiphase production wells, special tracers were introduced in the 1990s to move with only one phase, so as to give a phase-velocity log. Radioactive tracers with different energies are used to track the development of fractures, or other processes, in the multiple-isotope log. Tracer measurements are used qualitatively to determine the movement of fluids behind pipe, or quantitatively to determine fluid-flow velocity within the pipe.

See: flow profile,  flowstream,  injection well,  neutron capture,  production log,  radioactive tracer,  radioactive-tracer log,  tracer-loss measurement,  velocity shot measurement