There are principally two different injection strategies:

(i) Pulse injection: The full tracer volume is injected within a time period which is short in relation to its movements between injector and producer. In practice, injection times of up to several tens of hours may be considered a pulse injection. Most oilfield reservoir tests utilize pulse injection. There are various pulse injection procedures.

(ii) Continuous injection: A diluted tracer volume is injected by pumping continuously over time. The pumping speed is preferably adjusted to the varying injection water flow rate in order to keep a constant tracer concentration in the injected water. Injection times may be as long as one year or more. By knowing the injected tracer concentration and by logging the tracer concentration in each production well, the fraction of injection waters in the produced water from each well can be derived directly. Only a small fraction of injections are performed in this way.

There is also another point to consider in the injection strategy, whether to emply topside or downhole injection. If the well construction and completion allows for downhole injection, it must be considered whether it is feasible (technically and economically) or desirable to inject separately in each reservoir section (for stratified reservoirs). This latter method requires that each reservoir section can be isolated during the injection.

Most tracer injections are carried out as integral topside injections; the water (and the tracer) injected at the well head will enter the formation through perforations in the various strata in an quantity which is approximately proportional to the water-relative permeability of the various zones.