A Tracer is a substance used for tracing purposes.
Reference Definition by Schlumberger Oilfield Glossary in oil and gas explosion, A Tracer is a chemical or other material placed in the borehole fluid and later detected to infer information about the borehole or the drilled formations. The two main types of tracers used during drilling are the mud tracer and the filtrate tracer. A chemical or other substance placed in or around the borehole to measure fluid movement in injection wells. The two main types of tracers used during production logging are the bead tracer and the radioactive tracer.
