1. n. [Production Logging]

An in-situ measurement of the flow profile made by pumping different fluids down the tubing and casing and observing the interface between them. The fluids are normally both water, but one may be fresh and the other salty, or else one may contain some tracer, so that the interface can be detected by a production-logging tool. After the tubing is run to the bottom of the well, an interface is introduced by one of two methods. In the static method, the total flow rate is held constant and the relative flow rate of the two streams is changed. The location of the interface after each change is used to determine the flow profile. In the dynamic method, one fluid is pumped at different rates. The log was used in the 1950s and 1960s but is now used rarely, having been replaced by fluid-density logs and others.