The performance of many waterfloods [and enhanced-oil-recovery (EOR) schemes] is characterized by fluid injection under fracturing conditions. Especially when the geology is complex and the mobility of the reservoir is low, induced fractures can be of the same order as the well spacing, which has a significant (in general undesired) impact on both areal sweep and vertical conformance. Therefore, fluid injection needs to be actively managed and surveyed in order to design an appropriate injection strategy over time.

We have analyzed historical injection/production-test, injection step-rate-test, and falloff (FO) test (FOT) data of an existing complex waterflood in the Pierce field, North Sea. The mental subsurface model that emerged from this data analysis was developed further through a series of dynamic fracture-propagation simulations. While the data analysis was a relatively standard procedure, the fracture-modeling part was far from trivial and included simulations using a standalone fracture modeling tool and a more sophisticated coupled dynamic fracture-propagation reservoir simulator, both being in-house software tools.

The combined analysis was used to develop a better understanding of the waterflood performance. The main improvement compared to previous work was the integration of the data analysis and the dynamic modeling work rather than looking at each data source individually. In combination, a consistent explanation of the observed reservoir behavior was achieved. This has resulted in changes in the day-to-day water injection management and is expected to play a key role in longer-term development strategies