Various field data cases have been presented that emphasize particular aspects of performance of fractured injectors. These are:
WAG In some cases, Water-Alternating-Gas (WAG) has shown some effect in stimulating the reservoir, albeit usually relatively temporary.
Particle Size There was one data set received that included some information on the particle size distribution. While some basic information was missing, efforts were made to process this information to assess if there was any size dependency for plugging.
Temperature While it is uncertain that this is fractured injection, these data clearly show a reduction in the injectivity as the temperature increases, likely due to thermal alteration of the in-situ stresses.
Viscosity Viscosity changes with temperature and stress changes with temperature are competing mechanisms. Viscosity changes may be more important in soft formations although they were not in this particular instance.
Reservoir Pressure Two field examples are given indicating that it is crucial to make best efforts to measure, simulate or infer temporal variations in reservoir pressure.
Soft Formations Is it possible to fracture (either during injection or stimulation) an unconsolidated formation. Maybe. This example shows that you can at least inject above the total horizontal in-situ stress and that injectivity can be higher and stay high under these circumstances.
Acidizing This example is NAM1. It is used as a showcase in many places in these Best Practices, for two reasons. First, without carefully processing the data, converting to bottomhole conditions and taking out extraneous data (i.e., before a nonreturn valve was removed from the string), it was thought that this was injecting under matrix conditions. Later thinking strongly suggests that it was fractured injection. Secondly, the success of the acid treatment may have had more to do with cleaning the string than anything occurring in the reservoir.