Abstract
When hydraulically fracturing a horizontal wellbore with multiple perforation clusters, the fluid being pumped into the reservoir will preferentially take the path of least resistance. Perforations that are located in the lowest stressed rocks will take a larger amount of fluid, and those perforations located in highest stressed rocks will receive less, or in some cases none. One of the ways that engineers are trying to overcome these differences is the use of diverters. A fluid diverter is typically inserted at some point within a hydraulic fracturing pump schedule to seal off dominant fractures, allowing fluid to flow into under-stimulated fractures.
The problem with this methodology is that without reservoir knowledge, operators rely on rules of thumb developed through trial and error to determine when and how much diverter to use. Data has shown how this methodology can be ineffective, leaving some clusters over stimulated and others under-stimulated. Anecdotal evidence also supports these concerns because equally sized diverter slugs do not always have equal pressure response. This paper will present a methodology currently in use that examines well heterogeneity, and designs the diversion strategy based on actual reservoir properties. Estimations of minimum insitu stress at each cluster are combined with estimates of stress shadow effect both from previous stages and between treatment clusters to determine at which pressure each cluster will accept fluid. This data is then used to bin clusters into primary clusters which will be treated first, followed by a diverter slug, then secondary and possibly tertiary clusters. The volume of diverter slug used will be proportional to the number of clusters within the previous bin.
In addition to this, an engineered diversion strategy will look at the perforation design, fracture treatment design and pump rate. The result of this workflow is a tool that will maximize the effectiveness of diverters that will ultimately result in better producing wells at lower completions cost.
