1. n. [Production Logging]

A record of the change in temperature along a well, normally recorded by a fiber-optic cable. The distributed temperature is measured by sending a pulse of laser light down the optical fiber. Molecular vibration, which is directly related to temperature, creates weak reflected signals. These signals are detected at the surface and converted to a log of temperature along the well, sampled approximately every 1 m [3.28 ft] with a resolution of 0.1 degC. The fiber-optic cable is normally installed at the time of well completion, so that the distributed temperature log can be recorded at any later time without well intervention. Introduced in the mid-1990s, the technique can also be used to measure flow rates by creating a temperature transient and observing its movement along the well.

See related terms: flowmeter,  production log,  temperature log,  well flow rate