Flow distribution plays an important role in Produced Water Re-Injection operations. This is especially true when the injection horizon contains isolated hydraulic units that are individually capable of accepting part of or the entire injection rate. The hydraulic units maybe separated by an impermeable barrier, shale, and/or have variations in the minimum horizontal stress. Under normal operating conditions fractures initiated in one or more of these units would not intersect or combine. The fracture growth becomes a coupled problem where growth in one hydraulic units is dependent on growth or retardation in other units. Retardation might be caused by solid and oil deposition in the fracture that would plug its tip and damage its faces. Plugging would decrease available fracture length for leakoff below the actual total length of the fracture. Such scenarios become difficult to control if not initially planned or designed for and can lead to undesirable effects such as inefficient sweep or uncontrolled fracture growth.
In the following discussion the design and monitoring criteria for such problems will be addressed. We will review some available tools and prominent parameters and/or variables that affect this behavior both from a time dependent and independent point of view. Particular attention will be placed on the damage mechanisms, total suspended solids (TSS) and oil in water (OIW), and their effects on altering the injection rate distribution as a progressive time dependent phenomena.
Finally, two scenarios will be presented, as practical examples of field cases where flow partitioning issues presented a particular concern as a result of inherent reservoir properties.