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One powerful aspect of streamline simulation is the ability to create a snapshot of how the reservoir is connected at any instant in time, and how much fluid is allocated between injector/producer pairs. Because a transport problem is solved along each streamline connecting an injector to a producer, it is possible to related injected water volumes to off-set oil production. This novel information leads to the idea of injection efficiencies, which in turn can be used to manage flood more effectively.
Example field showing streamlines colored by injector. The resulting Flux Pattern Map for the same set of streamlines is shown at right, where thickness is proportional to the well rate allocation factor (WAF) which is the % of flow from each injector to the offset produces it supports.
Not only can the total flow rates between well-pairs be calculated and the WAF's derived, but individual phase rates can also be calculated between well-pairs. Knowing phase flow rates between well-pairs introduces the key concept of an injection efficiency, which is defined by as follows:
 EQ 1.Note the following about the above equation:
- There is an injection efficiency for each active injector in the field. The water injection rate is known (denominator), but the offset oil production (numerator) must be calculated using the information from the well allocation data supplied by the streamlines. On a per-injector basis this is the IEplot within studioSL.
- It is possible to define injection efficiencies on an individual producer/injector pair. Then both water injection and offset oil production must be computed from data supplied by the streamlines.
- The injection efficiency defined in Eq. 1. is a ratio of rates and therefore represent an instantaneous metric. However, the equation applies just as well to cumulative volumes, in which case the result would be an average efficiency.
- The definition of an efficiency can be extended to any type of injected and produced volumes and therefore can be used for gas injection as well as WAG injection.
  Above shows the Injector-Efficiency Plot for the 7 injectors at a given time. On the right is the same FPmap as before, but now the labels indicate the injection efficiencies along each well-pair connection (color is still by originating injector). Notice how some of the producers "see" vastly different injection efficiencies from different supporting injectors. In other words, sweep imbalances can be visualized on a per-producer basis (assuming a decent history match) and indicate patterns for optimization. | 
