Tracers can measure time spent by injected water or gas to arrive at producers. Combined with the injection rate of water this timing gives a direct measurement of the hydrocarbon volume replaced by injected fluids between any investigated injector-producer pair. The larger this volume is, the more efficient is the sweep.

Tracer data can therefore be used directly to quantify efficiency of an injector pattern or scheme. Measured sweep data from tracers integrates very well with reservoir simulation models and reveals inconsistencies in models in an efficient manner.