1. n. [Formation Evaluation]

An operation in which a logging tool is lowered into a borehole and then retrieved from the hole while recording measurements. The term is used in three different ways. First, the term refers to logging operations performed at different times during the drilling of a well. For example, Run 3 would be the third time logs had been recorded in that well. Second, the term refers to the number of times a particular log has been run in the well. Third, the term refers to different runs performed during the same logging operation. For example, resistivity and nuclear logs may be combined in one tool string and recorded during the first run, while acoustic and nuclear magnetic resonance logs may be recorded during the second run.

See: composite log