| abstract |
The present invention provides time released markers for use with single reservoir and commingled wells. The invention accomplishes the time release of markers by coating or encapsulating marker particles or by coating a proppant which has been saturated with a marker. After coating or encapsulation, the marker is injected into a well as is known in the art. The marker remains in the well. The marker is released after an elapsed of time. The elapsed time can be in a wide range. After the elapsed time, production is taken from the well and tested for the presence of the marker. Various types of known analyses can be performed to test for the presence and concentration of the marker in the production fluid. The concentration of the marker in the production fluid allows the apportioning of production from the reservoir. In addition, different markers may be added to each zone within a reservoir where each marker has a different elapsed time increment. The zones can be any different layer or area in the reservoir such as different strata or layer of rock, limestone or sand. Differing marker combinations allow contribution from different zones to be monitored over an extended time. |